Mobile Air Cleaners – A User’s Guide

A Trotec TAC mobile air cleaner

Mobile Air Cleaners – Background

A mobile air cleaner is the ideal solution to treating the air-borne dust that occurs in numerous work environments. Dust is always a nuisance but often a danger to health as has been well documented by others.  Whist many dust sources can be suppressed by modifications to cutting and grinding equipment, (for example with wet cutting on a circular saw or vacuum extract on guard ), there are still numerous small and medium sources of site dust that don’t have an easy method of local suppression. For example, smaller grinding operations, site joinery tools, core drilling, sanding, mixing of mortars, plasters and adhesives all contribute to the persistent fugitive dust that inevitably hangs within the enclosed areas of building sites.  It is easy to put in tool specific dust collection for some specific site tasks and also easy to control dust from the dusty industrial processes that are a permanent fixture. Controlling dust from unspecific temporary site work is ideally suited to mobile air cleaners.

Site dust from a refurbishment project could use a mobile air cleaner

Site dust from a refurbishment project could use a mobile air cleaner

The basic method of dust suppression is ventilation. The connection of some flexible ducting to a ventilation fan has been then a standard approach for years. But there are two problems here;

  • Firstly, the length of flexible ducting that standard ventilation fans can move air along is actually quite limited. Many loose a significant portion of their flow with anything more than about 5m of ducting. This limitation means the ventilation fan needs to be placed sufficiently near to an opening to outside for the duct to reach out.

  • Secondly if the work area is large and the outside is too far away with a vent fan you are just sucking the dust from one place and blowing it to another. Even if you are close enough for the duct to reach outside then the exhausted dust can be a nuisance to people outside the work area.

Mobile Air Cleaners – Approach

Puravent have been aware of this hole in the dust abatement armoury for some years so were delighted to find credible mobile air cleaners to solve this problem.  We offer a range of mobile air cleaners, which are easily moved from one site to another and plugged in to clear the fugitive dust in a room or other workspace. These mobile air cleaners combine a fan and various filters into a robust steel case, equally suited to building sites or industrial environments.

What appealed to us about these air cleaners was that there a number of sizes and filter types from fine filters right up to HEPA, so there is always a combination to suit most users. Also the fans inside are designed for the additional pressure imposed by filters, so the ability of these machines to blow through rather longer lengths of ducting is beyond doubt. Compared to straight forward ventilation fans, it is the additional flexibility that these mobile air cleaners provide which is key. They can even be used as a ventilation fan but without the filters and you have at your disposal, a substantial dollop of pressure to exhaust dust laden air along a much longer length of flexible duct.

The mobile air cleaner range consists of the following models;

Trotec TAC 1100 Trotec TAC 2500 Trotec TAC 4000
Trotec TAC 1100 1150m3/h Portable air cleaner

Trotec TAC 1100 1150m3/h Portable air cleaner

 

Trotec TAC 2500 2500m3/h Mobile air cleaner

Trotec TAC 2500 2500m3/h Mobile air cleaner

 

Trotec TAC 4000 4200m3/h Mobile air cleaner

Trotec TAC 4000 4200m3/h Mobile air cleaner

 

The choice of mobile air cleaner really depends on the type of dusty work being carried out and also the typical size of room that the unit would be used in. So if the dust is from general building, joinery, plaster dust and the usual type of site is domestic houses, then you might choose the TAC1100 because with a 1150 m3/hr capacity it can deliver the equivalent of 11.5 air changes per hour to a 100m3 room. This means that if you are working in a large domestic room then it will be processing the air in that room through a filter every 5 minutes or so. Obviously the larger the enclosed air space, the larger the duty that you require. But remember that there is a trade-off between duty and ease of handling i.e. no use having a mobile air cleaner that ideal for the size of air space but too large to be easily set up and used, better of with a smaller unit that at least will get used.

Rule of Thumb for mobile air cleaners

Assuming that the mobile air cleaner is to be used in a work environment, the air cleaner you choose needs to be able to deliver at least 8 air changes per hour in for the room(s) that it would typically serve.

It is important to remember that although these mobile air cleaners can be set to recirculate air in a room, they can also have ducting attached to either suction or discharge side. This means that you can extract air from one room, inducing fresh air to come in to that room, whilst the air cleaner is in another room and its’ exhaust into that room can displace dusty air through positive pressure treating the air. Essentially it is a way of treating two room at the time. Also with ducting and splitter boxes you can either extract dusty air and / or  deliver clean air from several rooms simultaneously.  This is important to factor into the choice of mobile air cleaner. Get a unit that can cope not only with the size of individual rooms, but big enough to handle the air cleaning requirements of all the rooms where dusty work is being carried out at one time.

Mobile Air Cleaners – Applications

Mobile air cleaners are ideal for controlling the following types of dust;

  • Asbestos dust
  • Quartz dust
  • Building rubble
  • Flour and wood dust
  • Mineral fibres
  • Mould spores
  • Paint particles

Ideal applications for mobile air cleaners include;

  • Sandblasting work
  • Building and conversion work
  • Water damage repairs
  • Fire damage repairs
  • Mould damage repairs
  • Asbestos remediation

Mobile air cleaners can generally take a variety of filters, depending on the type dust that you are trying to catch. Although most of these dusts mentioned above are relatively coarse, requiring filter classes ranging from G3 up to about F7, some will require a higher efficiency HEPA filter to catch the smaller particles. With a HEPA filter the range of dusts that can be safely removed increases to include; soot, viruses, metallurgical dust, fine asbestos dust, and pet allergens.  Selecting the right filter combination is not always straightforward. Please call us for help in identifying the correct filter combination for your application 0845 688 0112

Filters for Ventilation Fans

Although not strictly a mobile air cleaner, a combination of ventilation fan and filter can achieve much of what you would require in a mobile air cleaner. The penalty however is that ventilation fans are not high pressure machines, so the ability to move air, in quantity, through a duct is in most cases largely lost.   Some ventilation fans start with higher pressure and flow capability than others, and it is these ones that are best capable of being matched with a filter.

There are two types of filter for this arrangement. Either a filter canister which connects onto a duct, which in turn connects to the vent fan, or a filter sock, which is of sufficient diameter to connect directly to the fan. The canister type are easily wheeled about and have an end piece which can be opened to gain access to the filters inside.

Conclusion

Potentially harmful fugitive dust within work places and building sites can be safely controlled using mobile air cleaners, or filters attached to the more powerful ventilation fans. The choice depends principally on the size of the room that the unit will be used in, and we always recommend that the unit is selected to provide at least 8 air changes per hour. Choice of filters is a little more involved, so give us a call for guidance 0845 6880112

Guidelines and Regulations Concerning site dust (click title to activate link)

HSE publication  – Dust control on off cut saws used for stone and concrete cutting

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