Tech, Filtration Engineering Ltd, Air Filtration, Air Quality Control Systems, UK

To ensure the design or upgraded standard of air filtration is maintained it is essential to manage the following points:-

The use of low efficiency and poorly fitting filters can promote the build-up of dusts and microbial contamination in the HVAC system, and especially at coils, fan chambers and dampers. When wetness is added to the dust by way of moisture in the air, an unpleasant condition can easily develop. Filters of grade F7 (80-90% average efficiency on atmospheric dust) will remove the majority of dusts which may collect in an HVAC system, and also a high percentage of bacteria and retain them in the filter matrix. The air around us contains a variety of micro-organisms which we usually deal with through our natural resistance. However if they are allowed to grow in a suitable nutrient, micro-organisms multiply rapidly forming colonies which can be seen with the naked eye. Raising the air filtration standard to say F9 (95% efficiency) and ensuring that the filter framing system is airtight will increase the level of protection, but the benefit may not be noticeable in terms of reduced levels of micro-organisms within the controlled space. The key is efficient air filtration of atmospheric dust, a clean air supply and return air system and effective air distribution in the space. Supply air duct cleaning will not be required for many years (and possibly never) when filters of a minimum grade equivalent to 80% efficiency are installed.

Monitor filter life reduction (increase in differential pressure drop) using an analogue gauge of the ‘Dwyer Magnehelic’ design. A pressure switch only indicates when a filter change is required. Ensure the measuring points (pitot tappings) are correctly located.

Exhaust systems which are installed in snack kitchens, toilet, smoking and lobby areas generally do not require any form of air filtration. If a smell is generated by cooking, and the results cannot be discharged effectively, then a gas phase filter may be required. Mechanical filtration to F7 grade is essential for such applications to prevent coating the gas phase media which causes a rapid reduction in filter life.

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