The European standard EN 13779:2007 provides guidance on ventilation, air-conditioning and room-conditioning systems for designers, owners and users of non-residential buildings subject to human occupancy.
Its purpose is to achieve a comfortable and healthy indoor environment in all seasons with acceptable installation and running costs. It is now a national standard in all EU member nations and has actually been adopted as a law in Spain. The standard also specifies the required filter performance in a system to achieve good indoor air quality (IAQ).
When designing mechanical supply and exhaust ventilation systems, consideration has to be given to the quality of the outdoor air around a building or proposed location of a facility. Atmospheric dust and particles come in different concentrations and particle sizes, that have to be eliminated to fulfil hygienic and IAQ requirements. The same goes for the presence of potential allergens, carcinogenic pollutants from traffic, odours and gases. This is requiring the use of finer filters and for filtering outdoor air, recycled air and exhaust air.
This is why EN 13779:2007 now recommends a change to the classification of outdoor air (ODA), in which the former five-level classification system, ODA 1-5, has been changed to ODA 1-3 (ODA 1=Pure air which may be only temporarily dusty or polluted; 2=Outdoor air with high concentrations of particulate matter and/or gaseous pollutants; and 3=Outdoor air with very high concentrations of gaseous pollutants and/or particulate).
'Particulate matter' refers to the total amount of solid or liquid particles in the air, from visible dust to submicron particles. 'Gaseous pollutants' refers to carbon monoxide, carbon dioxide, sulphur dioxide, oxides of nitrogen and volatile organic compounds (VOCs).
This new outdoor air classification therefore has a direct impact on the choice of the minimum recommended air filter class in certain ODA categories, compared to those recommended previously in EN13779: 2002. The basic classification of Indoor Air (IDA) in the occupied zone, IDA1-4, remains the same (IDA1=high indoor air quality, 2=medium, 3=moderate and 4=low).
"This upgrade of EN13779:2007 is important for all of us and a main focus should always be on improving the indoor climate for healthier working and living conditions. Indoor environments in metropolitan, industrial and polluted areas, where people spend a long time indoors, have been generally upgraded to higher filter classes, and in many cases, with gas filtration," comments Jan Andersson, Camfil Farr's Product Manager for Comfort Air Filters in Europe and chairman of Working Group 4B Air Filters (WG4B) within Eurovent. Eurovent is the professional trade association for air conditioning, heating, ventilating and refrigeration manufacturers in Europe.
To carefully choose filters for air conditioning and ventilation systems help to safeguard human health by preventing airborne contamination from entering indoor environments.
Products for solid pollutants, for particle filtration, require one specific kind of filter standards. Filters for gas filtration, to remove molecular pollutants such as sulphur dioxide, nitrogen oxide, hydrocarbons, VOCs and ozone, has even higher requirements and differ somewhat in standard, design and efficiency. The selection of gas filter will depend on the concentration of harmful substances in the ambient air.
Impurities, gases and fine particles have increased in outdoor air, requiring a higher degree of filtration. Correctly specified filters are crucial for ventilation systems to function properly, to protect sensitive production processes, humans and the environment, and to improve indoor air quality, comfort and well-being. With the new recommended classification of outdoor air quality, EN13779:2007 specifies changes to the filter class required to achieve the preferred indoor air quality.
Other recommendations
EN13779:2007 continues to states that filters should be changed when clogged, as indicated by the final pressure drop, which is calculated and selected with regard to permitted variations in air flow, the filter's life cycle costs and life cycle assessment. However, filters in the first filter section should not be used for more than one year for hygienic reasons.
The recommended life for filters used in the second and third sections is no more than two years. Inlet air should be filtered in two steps (at least for IDA1 and IDA2), with the first filter in the air intake being class F5, but preferably F7.
The second step should be at least F7, but preferably F9. If one filtration stage is used, F7 should be the minimum requirement.
F5 filters are recommended for recirculation air to prevent contamination of HVAC system components and F5 filters to protect the extract and exhaust air system. Filters are replaced when the pressure drop reaches the specified final pressure loss, or when the hygiene interval is reached.m
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Peter Sandberg is CEO, Camfil Farr Power Systems, Stockholm, Sweden. www.camfilfarr.com
