The original purpose for having air filters in HVAC plant was to protect the plant and its operating efficiency. It is only in the last few decades that the priority of health protection of people in buildings has taken over as the primary purpose for these air filters.
The current condition and cleanliness of HVAC plant needs to be regularly determined as it can have a significant effect on the Indoor Air Quality of the building. Also needed is a visual inspection of the air filters to see if they are well installed, fit for purpose and in good condition.
The fine airborne particle pollution that damages personal health mean that air filters need to be a minimum F7 class filter for urban locations that have air pollution. (EN13779:2007 refers). As far as plant protection is concerned G4 rated filters were previously the norm. If HVAC plant filters are improved to F7 then the plant efficiency is protected more effectively than previously when G4 filters were used. Cleaner Indoor air quality will result from using good F7 class air filters.
To put filter performance in perspective an F7 class air filter has to typically be 8 to 10 times more effective at stopping fine particles that would pass through a G4 class filter.
These airborne particles pass through the HVAC plant and a proportion of them will deposit in the plant and associated supply ductwork. As far as plant efficiency is concerned any dust that deposits on coil heat exchanger surfaces is damaging to plant heat transfer efficiency and can clog the fins. Provided filters are effective and located upstream of coil heat exchanger components they will give protection.
This protection air filters give will be extended to any parts of the system in the downstream air flow so it important that good air filtration is located at the front end of the Air Handling system.
If deposits of dust are allowed to build up then there is a potential problem of growth of moulds and spores in the dust. Humidity and temperature are key factors that can enable growth. This organic growth can provide an opportunity for toxic gas emissions and the growth of bacterial colonies that contribute to poor Indoor Air Quality and an effect known as Sick Building Syndrome.
Air Filters therefore clearly play a key role in maintaining Indoor Air Quality by maintaining HVAC plant condition and preventing the potential for organic growth on the coils, in the AHU’s and supply ductwork.
HVAC air filters and ducting need regular inspection to ensure that building Indoor Air Quality is maintained. BS 15780:2011 is the new British Standard that advised the time periods between inspections based on building type and usage. Six monthly visual inspections are a good starting point if there are no other specific guidelines recommendations available.
To arrange an AC inspection of your HVAC plant visit www.ac-inspections.co.uk
As the market leading Air Filtration company in UK and the rest of Europe, we have been making surveys and inspections of complex HVAC and process plant filter systems for many years.
EN779:2002 to be updated in 2012