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Cruise Ship Infection Control

Cruise Ship Infection Control – Background

The headlines come round with a depressing and monotonous regularity. Canceled voyages, destroyed holidays, ships confined to port or not allowed into port, passengers confined to cabins. There is an ever increasing list of nasty, and some potentially fatal, infections that proliferate with ease in the confines of passenger carrying vessels. Cruise ship infection control seems forever topical. Currently there is the sad sight of scores of empty cruise ships bobbing about at anchor in various bits of sheltered water around the globe. Their owners are now presumably wondering if these vessels will ever see service again as we watch the ebb and flow of infections from Coronavirus. 

Vomiting bug, novovirus, and now coronavirus (COV-2) seem to be able to easily get a foot hold in the densely populated environment of cruise ships. These infections have various routes for transmission that are simply described as airborne (respirable) and fomite (from contaminated surfaces). The airborne route for the respiratory type infections is through the air in the form of the virus contained in airborne droplets (larger than 10 microns) and aerosols (smaller than 10 microns).  The paper (Mechanistic Transmission Modeling of COVID-19 on the Diamond Princess Cruise Ship Demonstrates the Importance of Aerosol Transmission) about the coronavirus tragedy which unfolded on the Diamond Princess makes informative reading about the various transmission routes on that cruise ship.

Cruise Ship Infection Control – Consideration of the Aerosol Transmission Route

The ventilation systems in ships conform to various industry standards which although in some respects are unique to the marine application, are in other respects very similar to the standards for buildings on land. Here you will find information about temperature regulation, ventilation operation, air change rates amongst other details but nothing on the prevention of air borne infections. This is a pity because the networks of ducting that supply air to the occupied spaces would be an obvious conduit for the supply of infectious bio-aerosols from one part of the ship to the other. In the methodology for effective cruise ship infection control, this transmission route warrants serious consideration.

Fresh air is ducted into cabins and used (potentially contaminated) air is ducted to the air handling unit. Then after filtration and other treatment a good portion can be ducted back to cabins or to communal areas after mixing with fresh air.

Air Recirculation. One problem is that in some air handling systems on ships air supplied to these occupied areas will be return air that has been mixed with a percentage of fresh air before being filtered.  The filters are not by the sort of thing that can catch airborne viruses. The filtered air is then distributed though ducting to the room spaces on the ship. 

Operators and builders of ships like those of large structures on land are under increasing regulatory pressure to be cleaner and more efficient.  So the efficiency of generating and retaining heat is important and this is why relatively warm return air is often recirculated.

Fresh Air. In more recent years air handling units are being fitted with heat recovery systems. This is a step forward because it means that air supply can be 100% fresh with heat being largely recovered from the outgoing return air. 

If the supply of air to the ships communal spaces and the cabins was 100% fresh, like for instance could be found in a typical modern hospital, then it would be logical to assume that the ducting could not be a conduit for the internal bio-aerosols. Yes… ?  Actually, no. 

Example of a Central Air Handling Unit. These are modular and can be built together on site to the customers specifications this package might handle 100,000m3/h dependent on operating conditions

But even with 100% fresh air through a heat exchanger there could still be an issues undermining the cruise ship infection control efforts.

Aerosol Transmission –  Problem 1 affecting cruise ship infection control

Heat exchangers can be one of a number of types. Cross-flow heat exchangers and ‘run around’ heat transfer coils ensure that the surfaces exposed to the outgoing air are kept separate to the surfaces exposed to the fresh air. Rotating heat exchangers on the other hand have a shared surface and that surface is huge. Rotating heat exchangers are very common in modern air handling units and can be found on ships. Rather than being absent from the cruise ship infection control strategy – out of sight out of mind – it needs to be front and central.

Let me explain…

Return air with heat and some level of bio-aerosol content passes through tiny flutes in the rotating wheel. The fluted wheel warms in the outgoing air and there is every possibility of bio-aerosols coming to settle on the surface of the wheel as the air passes through. The wheel continues to turn and passes into the supply air sector of the air handling unit. The wheels’ fluted surface complete with potentially harmful viral contaminant is exposed to the fresh air flow. It is perfectly possible for viruses to be readmitted into the ships ventilation ducts. 

A good reason perhaps to install in-duct UVC air purification to the supply air down stream of the wheel or an even better reason to, instead, purify the exhaust air before it passes through the flutes of the heat recovery wheel.

Aerosol Transmission –  Problem 2 affecting cruise ship infection control

With cruise ship infection control there is a problem with fresh air.  It is a mistake to assume air outside a ship is fresh and that there is no viable viral particles. If there are infected passengers, confined to cabins or in an onboard hospital then exhaust air from those areas will have viable viral particles. They will be typically exhausted to either the port or the starboard side of the ship.  On a reasonably still day the exhaust air from the ship will not readily disperse. In fact is likely to drift lazily past the open balconies of the cabins, or possibly to be lifted over the vessel to the other side, where the fresh air intakes are. In other words the source of viable viral particles in the fresh air is from the ship itself.

Another good reason to use in-duct UVC to purify the exhaust air being discharged from the ship so that at least you can guarantee that the fresh air is as free of viable particles as possible.

Cruise Ship Infection Control – Summary of Recommendations

  • If your cruise ships air handling systems supply fresh air only…
    • use in-duct UVC to purify the exhaust air upstream of the heat exchanger.
  • If your cruise ships air handling systems recirculate air…
    • use in-duct UVC air purification in the return air duct before it splits down to the exhaust and recirculation ducts. 

Cruise Ship Infection Control – The UVC Solution to Air Borne Contamination in Return Air

For decades UVC light has been used to kill biological contaminants in air moving through ducting, on cooling coils and even on food and pharmaceutical production systems. Its use in North America is so well understood and known about that it even warrants its own chapter in the ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) handbook. In the US it is even a requirement that air handling units fitted to public buildings in the US are fitted with UVC lamps to keep the cooling coils basked in UVC light.

Sanuvox Biowall - Ideal for cruise ship infection control

In-duct UVC fitting. Cruise ship infection control’s main weapon for ducted airflows.

Sanuvox Biowall - Ideal for cruise ship infection control

Air flowing past the array of in-duct UVC lamps deactivate biological micro organisms to a calculable and provable very high efficiency. The exact efficiency depends on the application parameters, however 99.95% on first pass is typical.

Yet, even with widespread acceptance and use in other sectors, there is barely a glimmer of interest in this technology from the marine and ship building market.

To those of us in the UVC supply sector the application of this technology in cruise ships is an obvious application. It is a complete ‘no brainer’.  Consider;

  UVC in-duct air purification is versatile and powerful tool to keep ventilation systems biologically clean.

  UVC in-duct air purification is very easy to fit and very cost effective to operate.

  Compared to investing in, retrofitting and operating a bank of HEPA filters in the air handling units, UVC in-duct air purification is more cost effective and more easily fitted.

UVC in-duct air purification has even been proven capable of keeping building occupants safe from terrorist attacks aiming to use building ventilation systems for dispersion of anthrax or other dangerous bio-aerosols (a far more challenging problem).

Why it is that cruise ship infection control specialists don’t use UVC in-duct air purification for the cruise ship ventilation systems?  It is a mystery. Meanwhile the cruise ships remain empty and at anchor for the foreseeable future.





Covid Safe Ventilation Of Buildings

Covid safe Ventilation of Buildings

As the ‘Lockdown’ is eased and staff return to workplaces there is an increased realisation of the need for adequate ventilation not only for worker and customer comfort, but also to minimise transmission of infectious diseases, including covid-19.

Covid safe ventilation of buildings is now understood to be vital to getting economic productivity growing again.

By ventilation, we mean the replacement of stale, and possible contaminated, air with fresh air from outside the building.  Although Covid-19 is the current issue, it is the same with any airborne viral contaminant. The air in the building is a potential conduit for infection from the infected to the uninfected. Continuous fresh air supply has the effect of diluting the viral concentration in the air. Buildings that are not ventilated enable the viral concentration to build over time.

Understanding that there is a need for Covid safe ventilation of buildings, the UK Health and Safety Executive (HSE) have issued Guidance on Ventilation and Air Conditioning during the Coronavirus outbreak which includes as its opening paragraphs:-

General ventilation. Employers must, by law, ensure an adequate supply of fresh air in the workplace and this has not changed.  Good ventilation can help reduce the risk of spreading coronavirus, so focus on improving general ventilation, preferably through fresh air or mechanical systems.  Where possible, consider ways to maintain and increase the supply of fresh air, for example, by opening windows and doors (unless fire doors). Also consider if you can improve the circulation of outside air and prevent pockets of stagnant air in occupied spaces. You can do this by using ceiling fans or desk fans for example, provided good ventilation is maintained.  The risk of transmission through the use of ceiling and desk fans is extremely low providing there is good ventilation in the area it is being used, preferably provided by fresh air.

Air conditioning.  The risk of air conditioning spreading coronavirus (COVID-19) in the workplace is extremely low as long as there is an adequate supply of fresh air and ventilation. You can continue using most types of air conditioning system as normal. But, if you use a centralised ventilation system that removes and circulates air to different rooms it is recommended that you turn off recirculation and use a fresh air supply. You do not need to adjust air conditioning systems that mix some of the extracted air with fresh air and return it to the room as this increases the fresh air ventilation rate. Also, you do not need to adjust systems in individual rooms or portable units as these operate on 100% recirculation. You should still however maintain a good supply of fresh air ventilation in the room.

The emphasis from HSE is clear. For Covid safe ventilation you need fresh air.

Covid Safe Ventilation – Long Term Solution or Short Term Fix?

Covid Safe Ventilation with a fan and flexible duct

A short term fix. Portable ventilator and duct. Fast, versatile and cost effective

This is the most topical of questions and it is exercising the owners and managers of work places and commercial spaces across the country and of course no one knows the answer because we don’t know how long the pandemic is going to remain a threat to our workplaces.

A short term fix to Covid safe ventilation is to use temporary ventilation. This can be as simple as using a combination of a portable ventilation fan and some flexible ducting. A permanent installed installation would require at least installed fan(s) and installed ducting.

But there are two problems, firstly to work out how much fresh air is necessary and secondly the loss of heat in winter.  In the summer the short term fix is easy – air may be introduced naturally via open door(s) and/or mechanically by using portable ventilation fan(s) either blowing fresh air in or pulling stale air out with the balancing flow coming via open windows and doors. However, as the summer draws to a close and the prospect of having to heat a large volume of fresh air looms large, attention is increasingly turning to permanently installed solutions complete with heating and/or heat recovery.

Covid Safe Ventilation – How Much Fresh Air?

In the UK, legislation exists setting appropriate standards for fresh air change rates. Building Regulations set out the minimum requirements for ventilation for new building construction. Approved document F (2010) expresses air change rates in a number of different ways:

      • air changes per hour.
      • litres per second (l/s).
      • l/s per m2 of internal floor area.
      • l/s per piece of equipment.
      • l/s per person.

The most commonly used expression of ventilation rate is air changes per hour and this terminology is widely used to guide ventilation rates for different types of application. The following table is generic and similar to others developed over the years before the current pandemic.

In the light of the Covid-19 pandemic of 2020 and the possibility of further waves of this and other Coronaviruses in the future, employers need to consider if their buildings offer the occupants Covid safe ventilation rates.

We have seen that many bodies representing different sectors are revising guidelines to specifically address their members concerns about Covid safe ventilation – dentists, healthcare, education, and building services to name but a few. The common thread to new Covid safe ventilation guidelines for the various sectors is that a far greater quantity of fresh air needs to be supplied.

In recent months we have discovered that even the basic ventilation rate of many buildings falls woefully short of even pre-covid guidelines (table above).  Building managers will need to work out if their buildings can offer satisfactory ventilation rates based on pre-covid standards, and if the current risk of covid-19 means that the rate should be increased.

Covid Safe Ventilation – Crunching the numbers

An example.  A room 10m x 10m x 4 m height has a volume of 400m3. If the room is ventilated at 1 air change an hour the resulting airflow is 400m3/h.  A higher ventilation rate of, say, 4 air changes per hour would mean an air flow of 1600m3/hr.  If the room is being ventilated at a rate of 100% fresh air, this means that there is 1600m3/hr of fresh air coming into the room.

However be aware that sometimes the term ‘air change rate’ is applied to ‘supply’ air.

Taking our example, if the room has 4 air changes of supply air and 25% is fresh, that means that 75% is recirculated through an air handling unit. So this means that the fresh air change rate is only 1 air change per hour. In terms of air flow it means that 400m3/hr of fresh is coming into the room and 1200m3/hr is being recirculated. The total supply to the room is 1600m3/hr. 4 air changes per hour supply, 1 air change per hour of fresh air, and 3 air changes per hour of recirculated air.

Covid Safe Ventilation –  Permanent Remedies

Across the country in buildings where there are mechanical ventilation systems, the air handling units are being adjusted to increase the ratio of

installed ducting can be part of a Covid Safe Ventilation system

Galvanised mild steel ducting

fresh air to recirculated air. In buildings where there is no mechanical ventilation employers must work out how to bring reliable large volumes of air into those building through open windows and doors using a variety of portable fans and flexible ducting.

duct fans are a vital part of a simple Covid Safe Ventilation system where there is no heat recovery

A typical duct fan from the KT range

But there is a problem as we move out of the the summer and into the colder seasons – if this fresh air is cold there will be either a huge impact on the comfort of employees/customers or on the heating bill of the owner/employer or both.  For some applications the additional heat will be within the capabilities of the existing system, however others will find that there is a heating gap to fill.

Any Covid Safe Ventilation system will need to introduce fresh air to the occupied space and this is where a huge selection of grilles and diffusers is useful.

Supply grilles

In cases where the Covid safe ventilation system is to be installed, in other words, a long term solution, a heat recovery ventilation system is well worth looking into. These typically have the exhaust air leaving the building through the same ‘box’ as the fresh air coming into the building. Inside the ‘box’ there is a heat exchanger that can reclaim 70% to 85% of the heat energy from the exhaust air and use it to preheat the fresh air coming into the building. As well as saving energy in winter they can also help cool the building in summer if you have air conditioning.

The big benefit to heat recovery in these uncertain times is buildings can be made safer by having higher rates of fresh air supply without a vastly increasing the heating and cooling cost.

Covid Safe Ventilation – Heat Recovery Solutions

Heat recovery using rotary heat exchangers can transfer bioaerosols from exhaust to fresh air. Not great for Covid Safe Ventilation

Thermal wheel heat recovery

Covid Safe Ventilation with heat recovery requires a counter flow heat exchanger

Counter flow heat recovery

This basic ventilation and heat exchange system comes in many forms and sizes from small commercial and domestic scale units right up to large industrial units. The smaller heat recovery units tend to use counter flow heat exchanger blocks, whilst larger heat recovery units tend to be fitted with rotating heat recovery wheels, also known as thermal wheels.


Mark ERV heat recovery

Our range starts with Mark ERV units.

Larger heat recovery ventilation is offered by Topvex air handling units.

These heat exchange mechanisms are built into machines of various configurations and sizes. Some are of a shallow profile and designed to be installed above ceilings to neatly hide the unit and ducting. Larger units such as the Topvex range are upright and would typically be floor mounted or perhaps hung form roof support structures.

Save VTX vertical has the ports in the top of the unit making it an ideal unit for smaller applications where it can be located in cellars or cupboards etc.

What these machines all share is some form of heat recovery, two fans (for the supply and exhaust flows), and some basic grade filters. The Topvex range offers further offers numerous options for heating, cooling, control and levels of filtration.

Topvex ceiling suspended air handling unit with heat recovery

We have over 250 options on our website – take the pain out of your search and contact us to discuss your specific needs.

Please contact us on 0845 6880112 or email info@puravent.co.uk with your project details.




UVC Air Purifiers – A credible new product

Puravent welcome a new range of UVC Air Purifiers

With current global pandemic causing a degree of mayhem in all markets it is perhaps no surprise that it is causing rapid changes in the air purification market. UVC air purifiers have up until 4 months ago been considered a bit niche particularly in Europe. Now, thanks to Covid -19, UVC air purifiers find them selves in the main stream.

Puravent - specialists at UVC air purifiersPuravent has been in the UVC air purification business since we started trading in 2003.  Our logo and name was even designed from the outset to reflect this specialism. Given our long knowledge the sector we are have always been fussy about what UVC air purifiers we offer to our customers.

However with the Covid 19 situation it became clear that we needed to widen our offering. The good news is that there seems to a plethora of new products that have arrived on the market in the last 3 months so there was a lot of choice. The bad news was that the vast majority of these product ranges were riddled with rookie design flaws and peddled with misleading sales literature. It has been a wheat from chaff exercise.  Luckily we have found the wheat and, stone the crows, we have added some mobile UVC air purifiers to our range.

UVC Air Purifiers range expands to include Sodeca

We are delighted to now offer the Sodeca UPM/EC range of UVC air purifiers.

There are a number of things that Sodeca have got right in the design that other manufacturers of UVC air purifiers have typically got wrong.

Sodeca UVC air purifiers exploded diagramAirflow Direction.  The direction of airflow in an mobile air purifier is important. The UPM/EC range has inlets that bring air in though the sides at the bottom of the unit. This means that particles, including airborne micro organisms are drawn downwards towards the floor rather than projected up wards into the breathing air of the rooms occupants.  Purified air is discharged from the top of the unit to the air strata in the room where it enters in the breathing air space.

Noise. The casing of the unit is made from acoustically insulated panels set into a box section frame. Also the fan which is the bit that generates the noise, is sandwiched between two filter stages which helps to suppress noise.

UVC Chamber. UVC air purifiers are all about delivering a dose of energy that can penetrate the DNA or RNA of micro organisms to damage the strands so that the spore, bacteria or virus is rendered incapable of replication.

That dose has two contributing factors. UVC intensity and time of exposure that the airborne micro organisms have to the UVC. The UPM/EC range cleverly locates its UVC lamps in the biggest void space in the unit which is where the air comes into the machine. This makes that UVC chamber and therefore the exposure time to the UVC energy as long as possible. That is brilliant when you consider that many UVC air purifiers in the market do not even have a UVC chamber!

UVC Dose. With the combination of lamps and the UVC chamber size, the UVC dose is high and the units deliver a 1 pass UVC dose above 45 J/m2. This means that the range has URV (UVGI rating values) of 15 or 16. This is good news because it means that it will deactivate many of the problem micro organisms including MRSA, influenza, SARS , Covid -19 and TB to as near to 100% as matters, in one pass.

Filter Choice. There is a clever choice of filters available. There are 3 different sizes of unit in the range and each size is available with either F7 and F9 filters or F7 and H14 filters. This means that you have a choice to have effective air cleaning above 95% of PM2.5 particles (i.e. those particles larger than 2.5 microns) or with the higher efficiency offered by the HEPA H14 filter you can remove greater than 99.995% of the most penetrating particles.

UVC air purfierCarbon Filter. The UVC frequency is not the type of UV that creates ozone and hydroxyls. This means that the UVC will not treat odours and volatile organic compounds on the airflow. The carbon filter stage however will capture these gaseous contaminants without the use of ozone.

Power. The two smallest units are powered by 230v single phase supply so will suit many office, retail and healthcare applications, i.e. suited to commercial air purifier applications.  The largest of the three sizes runs from a 415v 3 phase supply so will be ideal for industrial air purifier applications.

Airflow. The largest has an airflow of 3250m3/hr which is excellent for a mobile unit UVC air purifier. It means that in 500m3 air space it will deliver 6.5 air changes. That is great news because the air change rate (the relationship between air flow and room volume) tells you how often the air gets purified by the machine in each hour. With endless sources of air borne particles, air purification of this type is more about keeping air clean and pure on a continuous basis than purifying the air as single exercise.

In Summary

Good UVC air purifiers are relatively rare in the market, and good ones with sensible combination of filters, delivering an sensible dose of UVC onto a credible size of airflow are exceptionally rare. Delighted that we can now offer one such range to our customers. Please have a look at the Sodeca UPM/EC range in a bit more detail and call us if you need any more details.



HEPA filter & UVC? Or a choice of one or the other?

HEPA filter & UVC. A combination or a choice?

The Covid-19 peak appears to have passed and whilst there may be subsequent outbreaks we are encouraged to return to work and to reopen the economy. This has prompted employers across the country to investigate measures to make the work places safer. The purity of the air circulating around building ventilation systems and delivered into occupied spaces is now understood to be an important aspect of workplaces safety. Here we take a closer look at the choice between retrofitting HEPA filter and UVC to building ventilation systems, or to use one of the other of the technologies to ensure that air supplied into occupied spaces is safer.

Understanding Existing Filtration Capability

In choosing between HEPA filter & UVC in the quest to make buildings safer from Covid-19 it is worth firstly understanding how effective how effective the existing filters in a system are against the virus.

Mechanical ventilation systems that process the air supplied to, and extracted from, occupied spaces have typically been designed and installed with at the very least some filtration to protect the heating and cooling coils and the fan from dust accumulation. Often the filters will be a combination of a panel type prefilter, perhaps G3 or G4 efficiency followed by a F7 efficiency filter.

The size of the virus Covid-19 is widely accepted as being 0.12 microns, and looking at the graph you will notice that this size is in keeping with the larger size viruses (red dots) and that with F7 filters you could reasonably expect to remove around 25%. Worth also noting that even with F7 filters  you can expect some relatively high filtration efficiencies against larger micro organisms, particularly fungal spores.

Better efficiency filtration in air handling unit will go further than this and offer in the case of F9 filters, capture efficiency of over 95% of PM2.5. This goes a huge way to protecting building occupants from lung damaging dust, airborne spores, and bacteria. Viruses however are of a much smaller scale and typically less than 0.2 microns. Although fine filters such as F9 grade will catch some particulates of this size, the efficiency of fine filters of this type are not tested and rated against this scale of challenge.

HEPA minipleat

HEPA filter pleated media

The HEPA Filtration Solution

HEPA filters are tested against what is known as the MPPS (the most penetrating particle size). MPPS is generally accepted as being 0.3 microns and is the most difficult size to catch. The efficiency of HEPA filters at catching the MPPS depends on grade. With H13 being the lowest grade of HEPA having 99.95% or better efficiency up to H14 grade having 99.995% efficiency. These efficiencies are tested and easily demonstrable.

So if we know that the new bank of HEPA filters fitted in the AHU will catch 99.95% of the most penetrating particles, i.e. the MPPS (0.3 micron) we can be certain that the efficiency of catching Covid-19 (0.12 micron) will be higher because the efficiency at particle sizes smaller than the MPPS are greater.

The filtration performance of HEPAs is not in doubt as the standards to which they are manufactured and tested are rigorous.  However ensuring that the installation of the HEPA filters in the air handling unit has the seal integrity to ensure that the performance suggested by filter class is maintained, is far more problematical. The problem areas are inevitably the seal between the HEPA filter and its holding frame, the seal between one holding frame and adjacent holding frames, and the seals between the outer perimeter of the holding frames and the skins of the AHU.  Ensuring these seals are air tight and that there are no holes to allow 0.12 micron size particles to slip through is a challenge not to be underestimated.

Achieving the HEPA filter and holding frame is not the only installation issue. The pressure drop that a HEPA filter stage in the air handling unit will add to the overall system will be considerable and in order to retain the same airflow through the ducting system to the occupied spaces, it is certain that the fan will need to be run at a higher speed or it will require modification (replacement pulleys and belts)  or changing for one that can accommodate the additional pressure from the HEPA filters.

Once the fans have been altered or changed to suit this additional 600 Pascals of pressure (recommended change pressure for most HEPAs), the true cost of this increased level of filtration becomes apparent by the big increase in the running costs due to the increase in energy used by the fan.

uvc induct fitting

UVC in duct fitting

The UVC Solution

UVC does not catch micro organisms like Covid-19 virus like HEPAs do. But it can, if properly designed, deactivate micro organisms to efficiency levels comparable with the capturing efficiency of HEPA filters. But the problem is proving it. Whilst it is easy to measure particles in an air stream and test HEPAs, the same luxury of testing is not economically available to UVC. Instead for UVC the proof of efficiency is in the maths.

It is widely accepted that the quantity of UVC energy required to achieve a certain percentile deactivation of micro organisms is known. Tables containing UVC dosage for different micro organisms are always being refined and updated as new ones are identified. This information together with information about UVC intensity from lamps and the parabolic reflectors in which they are held forms the base information to a mathematical modeling program.

For each application we add the site specific parameters including duct size, airflow, temperature and the specific target organism (which these days is typically covid-19). An in duct UVC product selection is made and the % efficiency of deactivation on 1st pass and subsequent passes is calculated.  The maths is complex and even takes into consideration the material of the ducting as the different reflectivity of different materials has a quantifiable effect of on the efficiency of the UVC fixture in the application.

In duct UVC fixtures are normally installed down stream of the air handling unit, so they work in combination with the existing fine filters that are in the air handling unit. The effect is that the limited removal efficiency of the F7, F8, or F9 filters is complimented by the very high deactivation efficiency of the UVC array.

HEPA filter & UVC. A Comparison

 HEPA filter

  UVC air purification

 What does it do ? Catches particles including micro organisms and inert but never the less harmful particles such as soot particles. In other words filters are broad spectrum and bring wider benefit than just catching viruses. Deactivates airborne micro organisms including viruses, spores, and bacteria. When sized and designed for one target organism it will by default have increased efficiency on all those micro organisms requiring a lesser UVC dose and decreasing levels of efficiency on those requiring a larger UVC dose.
How efficient is it ? By EN1822 standard against MPPS  a…

H13 filter will be over 99.95% efficient
H14 filter will be over 99.995% efficient

Induct UVC array can be sized and specified per application to achieve over 99.95% deactivation on covid-19 and if required can be specified to as high as 99.995% deactivation.
Provable performance ? Provable by EN testing standards. Provable by standard UVC micro organism deactivation dosage information and application/product specific modeling.
Installation Holding frames installed into AHU. The effective sealing of frames to skin of AHU is critical to ensure overall efficiency of installation is as close as possible to the efficiency of the HEPA filters put in the frames. Integrity of the seal between the HEPA filter and the holding frames also important.

Additional pressure resistance from HEPA filters particularly when dirty will necessitate either modifications to, or change of the fan(s).


In duct UVC array is very quick and easy to install. It is installed ideally in the supply duct down stream of the AHU where it can benefit from relatively clean air afforded by the fine filters protecting the coils.

The array is mounted on a pair of struts that span the inside of the duct so that the UVC array sits central in the air stream and parallel to it.

The array is connected to a control panel that contains the ballasts that power the lamps.

Running cost The running cost to a bank of HEPA filters comes from;

a. the periodic filter changes that will be required.

b. the pressure drop range of around 200- 600Pa though the life of the HEPA will cause increased energy use and of cost.

The running cost to an induct UVC array comes from:

a. the periodic lamp changes  that will be made ever 2 years or so.

b. the power to the array of lamps (about 260w) will cause a modest increase in the cost of treating the airflow. However there is almost no pressure drop burden to affect the power consumption of the fan

  • Catches inert particulate matter as well as micro organisms so wider scope of benefits to building occupants
  • Fraction of the running cost compared to a bank of HEPAs. When factoring filter changes, lamp change, it is typically only 15-25% of the cost of running HEPAS
  • Very easy to fit in ducting
  • Expensive, costly and fiddly to install as more work needed for holding frames, seals and fan modifications
  • Might not be space in AHU to accommodate a bank of HEPA filters
  • Costly to run
  • UVC does not catch particles. It only deactivates biological particles
  • Care needs to be taken if installing in air handling units to protect plastics within AHU from direct UVC light and to have door interlocks to prevent direct sight of UVC in operation


HEPA filter & UVC

MPPS and the gap filled where the filter efficiency dips

HEPA filter & UVC used in combination

Using both in combination is the ultimate in belt and braces approach.

If you put the UVC array upstream of the HEPA filters then the effect is to disable the micro organisms before catching them in HEPA filters. To put the UCV array after the HEPA filters is basically using the UVC to  deactivate the very small portion of micro organisms that pass through the HEPA (in the order of 0.1 – 0.01%)

The graph (left) shows fractional efficiency of MERV (Minimum Efficiency Reported Value) rated filters. Although this does not correlate directly to HEPA filters It does serve to demonstrate the dip in efficiency at the MPPS. The same dip happens for HEPA filters but to a lesser degree and it is micro organism particles represented by this gap (the hatched area) that UVC downstream of a HEPA would be deactivating .


HEPA filter & UVC – Consider the purpose

If the purpose of the modifications to the air handling system is to make the supplied air safer from airborne micro organisms and if with the existing fine filtration (F7, F8, or F9) in an air handling unit, together with a properly specified UVC induct array can achieve an efficiency of at least 99.9% against Covid-19 then the thorny question has to be asked;

  • What is the point of adding an additional cost of HEPA filters, their installation and their heavy running cost? 

But equally, if the purpose of the modifications to the air handling system is to make the supplied air safer from all particles including inert sub micron size particles, then;

  • What is the point of adding an additional cost of a UVC array if the micro organisms they are trying to deactivate have already been caught up stream or will be caught in HEPAs downstream?

HEPA filter & UVC used in combination in mobile air cleaners

It is worth mentioning that there is a trend for portable/mobile air cleaner units that have both HEPA filter and UVC. These tend to follow a well trodden path originally set by the domestic air cleaner world which is that  is that ‘features’ sell. ‘HEPA’ is regarded as a feature, as is ‘UVC’ and they are seen by the unwary market as ‘must have’s.

In the Covid-19 world, given that the objective of both of these is the same in that you are looking to reduce the quantity of viable aireborne coronavirus particles, then is strange to demand that an air cleaner must have both features. The problem is that many of these type of units have token gesture HEPA filters and token gesture UVC. In other words the filter and its holding frame can be untested, full of holes and unsealed to the air cleaner body, whilst the UVC is likely to be pitifully inadequate to treat the air flow to any credible level of efficiency. There are however exceptions. We have scoured the market and added a range of credible air purifiers from Sodeca to our line up. This range has been recently developed and seems to avoid the glaring design errors that plague the vast majority of products in the sector.

HEPA filter & UVC – A Summary

  • There is no clear winner between the two because they both have merits and ideal applications, indeed they can even be used in combination if there is a need to fill the efficiency gap in the HEPAs inherent weak point i.e, at the MPPS.
  • The HEPA filter solution catches all particles to understood levels of efficiency but that ‘catch all’ capability comes at an eye watering running cost and more often than not a significant complexity and costs to the retrofit.
  • In duct UVC arrays deactivate biological particles ensuring they are incapable of replication, in other words rendering them inert and the running cost is limited to running the lamps and replacing them every 2 years. They are a doddle to retrofit into ducting and require no fan upgrading.


In-Duct UV-C Air Purification – A Beginners Guide

Two Sanuvox Biowall in-duct UV-C arrays in a duct section

Covid-19. The topical challenge

The task of sourcing commercial in-duct UV-C air purification equipment for the first time can be bewildering. There is a wide array of options for what is a complex technology to treat an airborne problem that you cannot see but which you know will be there.

It is a lot to grapple with and the potential for making an expensive and ineffective mistake is high.

In this Covid-19 era the air purification market is a jungle. This guide will help you avoid the pitfalls and to find a system that will be effective and which has a known performance efficiency in your particular application.

Avoid the in-duct UV-C ‘Elephant Traps’

  • Specifying a UV-C system to treat an air flow in a duct is NOT a simple process. If your potential supplier asks little but just says you need a ‘Whizzo bug blitzer 34X’ or whatever, find an alternative supplier. The ‘Barry from Cillit Bang’ approach to selling UV-C equipment should ring very loud alarm bells. It is the No.1 clue to spotting the clueless supplier.
  • If your potential supplier does not specify the In-Duct UV-C equipment specifically to your application, find an alternative supplier.
  • If your potential supplier is pumping out 99.999% etc. efficiency claims without clear and stated context of the exact conditions in achieving the claimed efficiency, find an alternative supplier. The efficiency of all in-duct UV-C systems are dependant on the parameters of the application in which they are used.
  • If your potential supplier does not ask you about the following details of your application, find a different one that does.

The In-duct UV-C Variables

The variables for treating air-borne micro-organisms with in-duct UV-C are as follows;

  • Air flow. We need to know what airflow is moving through the duct.
  • Duct dimensions.  We need to know the width and the height of the ducting, or if it is round duct, we need the diameter. This information is vital for calculating the air speed through the duct and past the In-duct UV-C equipment. Also we need to know the straight length of duct where the in-duct UV-C is to be fitted. This is so we know how much available length there is to accommodate the equipment
  • Duct materials. The inside surface of the ducting is a vital of often overlooked aspect of in-duct UV-C design. The materials that are best for reflecting white light are a very poor guide to the materials that are suitable for reflecting UV-C light. For instance stainless steel has UV-C reflectivity of 20%, galvanised mild steel 57% and aluminium 85%. The material, and therefore the reflectivity, of the duct walls has a large impact on the efficiency of the system installed and therefore affects how much UV-C we specify.
  • Target micro-organism. There are hundreds of different types and each has a known amount of UV-C dose required in order to achieve its deactivation to a particular % efficiency. The amount of UV-C required for different viruses, bacteria and spores varies over a very large range. For example if you are looking to achieve 99.99%, 1 pass deactivation on Covid-19, we would be specifying an in-duct system that can deliver at least the required dose of UV-C to treat Covid-19 to this efficiency.  But that same system will also treat the other airborne micro organisms present to a greater or lesser efficiency. We have lots of tables of this type of information and can show how a target ranks in amongst others so you get a feel of the overall effectiveness of the specified in-duct UC-V unit for different challenges.
  • Air temperature range. The output from UV-C lamps varies depending on their temperature. If we know the air temperature, we can adjust the selection of unit to suit.
  • Upstream filtration efficiency. For specifying an induct UV-C system we need the air to be filtered to ideally F7 standard. This ensures that the air is clean enough to minimise dust settlement on the UV-C  lamps, which would otherwise impair their UV output. If there are HEPA filters upstream then this is useful to know because it narrows down the definition of the challenge and we can factor in the HEPAs effectiveness at catching the target micro organism with the in-duct UV-C efficiency at deactivating those that the filters do not catch.
  • Duct function. What we mean by this is – what kind of air is the duct carrying? Fresh, recirculated air, or a mix of both. Understanding this impacts the unit selection.

What to look for in the product selection

A product selection for a particular application will include;

  • The quantity and model of in-duct fitting with dimensions.
  • The recommended placement within the duct section with dimensions.
  • The air velocity of the air passing the UV-C array.
  • The minimum, maximum and average UV-C dose mJ/cm2 delivered to the passing air.
  • Input power to the UV-C array.
  • The efficiency of the UV-C array in your application for the chosen target airborne micro organism(s), at first pass and successive multiple passes..

Features to look for in a in-duct UV-C air purification unit

  • Lamps must be in direction of airflow.  There are a number of reasons for this.
    • The operating temperature of the lamp will be maintained at a much more even temperature and will not suffer wind chill effects and cold spots typical of UVC lamps at right angles to the airflow. A uniform operating temperature is critical to ensuring ensure a longer life for the UV-C lamp.
    • Lamps parallel to direction of air flow ensures  highest possible UV-C  dose from the lamps because of longer ‘dwell time’.
    • Safer – Lamps parallel to air flow are far less prone to being damaged or broken should debris inadvertently be carried on the airflow.


parabolic reflector

Parabolic reflector is vital for utilising all the UV-C light generated by the lamps

  • Lamps must be supported and held with in a parabolic reflector ideally made from extruded aluminium section.
    • This ensures that all the light emitted from the lamp fitting is used and projected to best effect through the passing airstream. Without a parabolic reflector it is similar to a torch bulb without a reflector i.e, feeble
    • The reflector provides rigid protective support for the lamp both in transport before installation and in use in the duct.
  • The array of lamps should be sufficient to ensure that the complete face area of the duct is basked in UV-C light for the complete length of

    outward projection of UV-C light to duct walls

    Outward projection of UV-C light to inside of duct walls

    the fixture.

  • The system should have a control box;
    • complete with ballasts to run each of the lamps in the array.
    • with dry contacts to allow for connection of BMS.
    • should have contacts to allow connection of safety door switch.
    • should have connection socket to allow a remote monitoring with a control screen.

The in-duct UV-C array should have strong mounting struts

  • The array of UV-C lamps should have a robust support structure for secure fitting in the duct.
  • The option to fit self adhesive aluminium lining to the inside surface of the ducting. This has a very significant impact on the overall efficiency of the installation




An in-duct UV-C should look like a Sanuvox Biowall.

Sanuvox Biowall In-Duct UV-C air purification

It’s called Biowall for a reason!

Call or email us to discuss your in-duct UV-C application.



Coronavirus – Service Update Letter

Dear Customers,

The team at Puravent very much hope that you are managing to keep clear of the dreaded Covid-19 and are coping as well as can be expected with the ‘new normal’.

Having been locked down with the rest of the country and on a rather restricted ‘operate from home’ operation, I am delighted that we are now back and operating from our office and normal service has been resumed.

Thank you for taking the time to visit our website and your interest in our products.

Stay safe.

Yours sincerely,




Bill Anderson


Coronavirus Infection Control

Coronavirus Infection Control Using 3 Of The Best

Extraordinary circumstances push me to be blunt in this blog, indeed far more direct than I would normally be comfortable with, so before you start muttering about Puravent jumping on a bandwagon and milking what is an increasingly alarming public health situation you might want to consider that Puravent has been operating in the field of air purification since 2003 and has been supplying Sanuvox equipment since 2006. It is something we are experts on and something that others need to understand a whole more about in order to slow the spread of Coronavirus Covid-19.

As we look down the barrel of national lock down, let me quickly ‘cut to the chase’;

1. If you want to prevent active Coronavirus Covid-19 being transferred in an airstream along ducting and into occupied spaces….

           ….you can not do any better than to use Sanuvox BioWall

Coronavirus Infection Control using Sanuvox BioWall in duct air purification

Coronavirus infection control using Sanuvox BioWall in duct air purification

2. If you want to effectively and very quickly sterilise intensive care units (ICUs) or isolation rooms between the occupancy of one patient and another then….
           ….you can not do any better than to use Sanuvox ASEPT.2X

Room sterilisation using a Saunvox Asept.2X mobile UVC sterilisation pods a key tool for Coronavirus Infection Control

Room sterilisation using a Saunvox Asept.2X mobile UVC sterilisation pods


3. If you want to effectively minimise the spread of Coronavirus Covid-19 amongst occupants of a room such as, an office, a communal area in a care home or a class room then….

          ….you can not do any better than to use Sanuvox P900GX air purifiers

Coronavirus Infection Control in shared indoor spaces

Sanuvox P900GX Coronavirus Infection Control for shared indoor spaces, such as schools, offices and care homes


If you are interested in a bit of detail, keep reading.

Coronavirus Infection Control with UV – A bit of detail

How do these Sanuvox air purification systems work?

They are very cleverly engineered to use high intensity UV light to kill viruses, bacteria and even spores.

Is this new technology?

No, its been about for many years but not widely adopted in UK and Europe.

How does UV work?

UV light is the most effective way of deactivating airborne biological contaminants, including spores, bacteria and viruses. UV light at the specific wave length of 253.7nm is the very best at this task.

UV light at 253.7nm is best at breaking the DNA strands in viruses, bacteria and spores, and this ‘deactivates’ them preventing them from proliferating.

But don’t most air cleaners have UV light as part of their functioning?

Some air cleaners do but Sanuvox do not make cheap air cleaners. Instead they make the very best commercial UV air purification systems. UV air purification systems and air cleaners do very different jobs and comparing them is a bit like trying to make comparison between space ship and a pork pie.

So how difficult is Coronavirus infection control using UV?

The obvious bad news is that Covid-19 is very easily spread by touch and in air. It is also unfortunate that so little attention thus far has been given to minimising the airborne spread of the virus in controlled indoor environments. The good news is that Covid-19 like other variations of Coronovirus is easily treated on air using UV light. This means that the UV dose that is needed to break the DNA strands in Covid-19 are small relative to many other biological contaminants.

So what is so good about these Sanuvox products?

In a word – dose.  Germicidal UV dose to be precise.  Accepting that the Sanuvox UV lamps are engineered to deliver UV light at 254nm the ‘dose’ is about 3 factors

1. Surface area of the UV emitting surface i.e. the surface area of the UV lamp. The more surface area a lamp has, i.e. the larger it is, the more germicidal UV light it can emit.
2. Intensity of the emitted UV. This is about quality of the UV lamp.
3. Duration. i.e. how long the virus is exposed to the intense germicidal UV.

By getting these factors right Sanuvox ensure that their well engineered products deliver a massive dose of germicidal UV to guarentee a very high kill rate on a wide range of biological contaminants.

Coronavirus Infection Control – What Next?

There are no guarantees of complete Coronavirus infection control with Sanuvox or indeed any other infection control products. It is, however, about signifficantly changing the odds and by using Sanuvox systems you at least know that you are making the best bet available for UV infection control.

If you want to find out more about Coronavirus infection control in;

• air moving through ducts
• the air in rooms such as offices that do not have mechanical ventilation
• ITU (intensive care units) and other patient care rooms

….then please call us to discuss the suitability and supply of Sanuvox infection control equipment.

Thank you.



Wall Mounted Industrial Fan Heaters

Electric wall mounted industrial fan heaters don’t perhaps get the attention they deserve. Shame because they are a very easy and effective way of heating smaller working environments.

When most people think about wall mounted fan heaters, what comes to mind is a small domestic 1.5kw or 2kw unit with a pull string, whereas we like to think a bit bigger. In fact we don’t do domestic ones, only industrial wall mounted fan heaters where they can easily be large enough to deliver 30kw of heat.

Panther heaters operate with a remote controller and thermostat controlling up to 6 heaters
Heat/fan speed Contoller
TAP16 Thermostat

Advantages of wall mounted industrial fan heaters versus a portable fan heaters?

CAT heaters range covers up to 9kW

Whatever the size of wall mounted fan heaters their great advantage is that they are easily installed and once on the wall and connected up, they are out of the way. Although there are plenty of different models of portable heaters, and some of them excellent, there is the ever present power lead and the chore of moving it out of the way when you need the bit of floor that it is on, for something else. Whereas portable fan heaters tend to get moved around for best effect on work areas within in larger buildings, wall mounted fan heaters are better for whole room heating in smaller working environments. This means that in workshops, small industrial units, laboratories, shops, consulting rooms and the like, electic wall mounted fan heaters are ideal.

Wall mounted industrial fan heaters – single phase

A conventional 230 v single phase electricity supply is a little limited for the purposes of heating work environments. In broad terms 230v supply limits your choice to heaters that are not much bigger than 3kw. Whilst this may be ok for very small applications, once your heating requirements demand multiple 3kw heaters, you will very quickly run into limitations on the capacity of the power circuit that you might have been planning to plug the heaters into. When faced with this limitation many customers investigate the costs of installing a 3 phase supply.

Wall mounted industrial heaters – 3 phase

As with any other electic heater type the availability of 3 phase supply opens up the potential options hugely, compared to single phase. For most industrial environments where there are electrically driven machines 3 phase is not a problem, all the machinery will operate on 3 phase and the 3 phase circuits will be in place. The existence of 3 phase not only opens up the range of heaters available but also the range of heating capacity that is available and with up to 30kw generally being the upper limit on 3 phase wall mounted heater capacity.  With that size of heater available there is scope to heat really quite large industrial and commercial working environments using these heaters, but in reality when the application size is of this size running costs have much more impact and tend to outweigh the electic wall mounted heaters ease of installation and modest capital cost.

Industrial wall mounted industrial fan heaters for challenging environments.

Many working environments are challenging to heat because of dust, vibration, damp or corrosive atmospheres. The easy availability of wall mounted fan heaters specifically designed to be compatible with these type of environments make this type of heating an easy option and more attractive than more complex and expensive alternatives. 

Elektra industrial wall mounted fan heaters for extreme environments
Elektra wall mounted fan heaters for extreme environments

For these difficult applications we tend to look first at the Elektra range of heaters.  These heaters can be either wall mounted or free-standing – the bracket doubles as a stand when on the floor, and there are sub ranges suited to damp environments/ vibration/ dusty and fire risk environments and for producing elevated heat levels.  The Elektra heaters are well certified and versatile

The way the Elektra heater range works is as follows.

Application typeDamp and or
corrosive environments
 Marine  Dusty and/or
increased fire risk
Needing elevated heat
Outputs/supply3kw/ 230v
6kw/ 400v~3ph
9kw/ 230v~3ph
15kw/ 400v~3ph
3kw/ 230v
3kw/ 400v~3ph
3.6kw/ 440v~3ph
5kw/ 400v~3ph
6kw/ 440v~3ph
3kw/ 230v
6kw/ 400v~3ph
9kw/ 400v~3ph
6kw/ 400v~3ph+N
9kw/ 400v~3ph+N
Insulation classIP65IP44IP65IP44
Approved for use in combustible area
Useful featuresOuter casing in acid proof steel2 of the 3 phase models may be run from 60Hz supply. Vibration Resistant.Relatively low element temperature makes it ideal for dusty environmentsHigher temp. safety cutouts than standard enable much higher output temps.

Ethylene Removal by UV

Ethylene Removal by UV might seem like a strange title, but Ultra Violet Light is an effective method of controlling  ethylene in fresh produce storage and processing facilities.  Like other more traditional technologies like dry chemical scrubbing, the UV installation needs to be properly engineered and set up, but once in use the big benefit of using UV is its very low running costs.

Fruit cold store

The storage and processing of fruit and vegetables is a finely orchestrated battle against time. Most products do not linger in storage for long and in many processing facilities the time spent from ‘goods in’ to ‘goods out’ is measured in minutes, rather than hours. The investment in machinery to make this slick process so effective can not be jeopardized by anything that can have an adverse effect on the self life of the finished product. Competitive advantage is defined by freshness, speed from field to shop and shelf life.

Ethylene produced by the decomposition process in fruit and vegetables in turn stimulates decomposition in fresh produce, and it is vital that where unprocessed produce is held in storage ethylene is controlled, to ensure that the freshness is preserved and that waste from the process is minimised.

Ethylene Removal the old way

Traditional ethylene removal often uses dry chemical scrubbers. These machines generally have a prefilter, a chemisorption bed and an after filter. These stages make for quite a high pressure drop for the onboard fan to overcome in order to move sufficient air through the machine. With any system using a fan, pressure drop has a direct effect on running cost related to electricity consumption. The power costs, replacement dry chemical media costs and the down time cost of changing the filters and media, make the overall running cost of the traditional scrubbers relatively high.

Ethylene Removal the UV way

UV ethylene removal is totally different, and is ideally suited to the cool, humid environments typical of fresh produce storage. UV light at 187nm wave length is very effective at oxidising airborne chemical contaminants such as ethylene. The key is to ensure that there is the correct balance between the intensity and exposure of this wavelength UV and the volume flow of air being treated.  187nm is known as UVV light, and it has the characteristic of making oxygen react with chemical contaminants and in treating ethylene, it oxidises to produce carbon dioxide and water vapor.

 C2H4 + O*  CO2 +H2O

Using UVV for ethylene removal is easy and there are generally two methods.

Cold room with evaporator cooling. One option for treating Ethylene is to fit UV system inside the evaporator housing

Firstly the UV lamps can be incorporated into existing chillers or air handling units serving the room. In this method the spliced lamps are arranged to bask the cooling coils in UV light, which not only ensures that ethylene passing through the coils is oxidised, but also that the UVC light which is germicidal, prevents any biomass slime forming on the coils.

coil cleaners in evaporator box
Coil cleaners in evaporator box
Sanuvox Quattro is the ideal basis for an ethylene removal system

The second method is to use a UV lamp array such as a Sanuvox Quattro or Biowall in a purpose-built scrubber. Unlike the dry chemical scrubber these units are quite lightweight and are usually assembled from standard ducting components and ancillaries. The UV lamps in this case will also be ‘spliced’ thereby combining the germicidal merits of UVC light and the ethylene oxidising property of UVV light. The scrubber complete with its own axial fan and inlet filter is usually suspended from the ceiling or can be mounted above the ceiling with just inlet and outlet grilles showing inside the room.

Because the upsizing of UV based ethylene removal systems is relatively cheap there is every reason to provide sufficient sizing for these systems for any given application from the start. In Contrast dry chemical scrubber systems  are heavier and more expensive which creates the temptation to cut corners in design and sizing.

Ethylene Removal System suspended from roof structure

Ethylene removal by UV also has much lower associated pressure drop through the scrubber so that even when the power of the fan is combined with that of the lamp ballast the power consumption will typically be only 1/5th or 1/6th of that used by a chemical scrubber handling the same airflow.

Maintenance is an important consideration and although lamps will periodically require changing, it is a very easy, quick and clean procedure. UV based systems ensure that it is not just an ethylene removal system. The germicidal UVC part of the lamps will ensure that airborne spores bacteria and viruses are controlled as well – something that dry chemical scrubbers just don’t do.

Ethylene Removal with UV  – Summary

UV based ethylene removal uses both UVV and UVC, which means that it not only removes ethylene but also controls airborne fungi mould and spores. This means that as well as the stimulant for ripening being controlled but also the biological contaminants associated with rotting are controlled. Ethylene removal with UV is;

  • Very effective
  • Clean – does not cause dust
  • Low running cost
  • Easily scalable
  • Easily maintained
  • Can be controlled by gas monitors
  • Can be linked to BMS
  • Is suited to humid environments
  • Also controls biological contaminants
  • Can be fitted within evaporator housings, or free hanging

For further help on ethylene control, call us –  01729 824108

Are you Wasting Heat and Energy?

Investing in destratification fans pays back instantly in terms of worker comfort also pretty quickly in terms of £££s as its puts an end to wasting heat and energy. Destratification fans can be retro-fitted to almost every workplace with immediate benefit.


Frico 9kW wall mounted fan heater

We recently quoted for a couple of Frico 9kW unit heaters to a client to heat his small manufacturing unit.

We also quoted for a thermostat to control the heaters and help to minimise his energy bills.


Room thermostat


Airius destratification Fan

To complete the offering we quoted for a small Destratification Fan to further minimise the bills by returning rising hot air from the ceiling of the factory to the working area (i.e. where the people are).

The client went ahead and bought the heaters and thermostat but did not proceed with the Destratification Fan.

A few weeks later we got a message to the effect that the heaters were working flat-out, the ceiling space was toasty (wasting heat and energy), but the workers were still cold! After some discussion the client decided to buy and install the Destratification Fan albeit with a little scepticism.

Today we got the following message and photographs…..

Hi Bill/Robert


Two heaters and a destratification fan in use in a small manufacturing unit

You will be happy to know that the Airius 15 destrat fan is working a treat !

Heating is actually switching off now.  Fingers crossed the bills reduce too.

Appreciate the help and advice. Attached photo which you can use if you want.

…and here is the photo they sent, with the two heaters wall mounted with isolator switches towards the right of the photo and the fan hanging from the ceiling joist near the centre.

We have hundreds of heating and ventilation options available on our website so if you require any assistance please do call us to discuss your requirements on 01729 824108. Alternatively email through your enquiry to info@puravent.co.uk or follow us on Facebook or Linked In

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