Ventilation for non-residential buildings

For outdoor pollution, the standards still uses PM10 (diameter of particles up to 10 micron) as a reference parameter. However, in order to protect health, there is a growing belief that it is necessary to focus on much smaller particles. For gaseous pollutants, the standard refers to the concentrations of CO2, CO, NO2, SO2 and VOCs.
As a guide, the following table associates the level of outdoor air quality to the (yearly) concentration of pollutants mentioned and the geographical area:

The classification of the air inside the building is divided into 4 categories, from IDA1, the highest quality, to IDA4, which indicates low-quality indoor air.
It is impossible to provide an exact definition of the categories, as this is related to the nature of the polluting sources and people’s different perception or health effects. A practical classification method is based on the concentration of CO2, which is a good indicator in terms of the release of human bio effluents, but for the absolute quantity of air. For an indication of the required air flow for an adequate quality of the air, one can use another indicator, the rate of outdoor air per head.
The table below briefly shows the classification of the quality of indoor air in accordance with the practical methods described above:

Recommended filters in accordance with EN 13779.

EN 13779 clearly specifies the required filter class to achieve the desired quality of indoor air. Filter classes are expressed in accordance with EN 779:2002. EN 13779 also shows that, for instance, if you are in the city centre and you want medium or high quality indoor air, a filter for solid particulate is not enough. A filter that traps gaseous pollutants is also required.

The EN 13779 standard also provides information about when the filter must be changed:
“The filters must be replaced when the pressure drop reaches the specified final pressure drop or when the specified hygienic conditions are no longer met, if this occurs earlier. If it is possible to anticipate the hours of operation of the system, these can be used as a criterion for changing the filters as follows:
– the pre-filter must be replaced after 2,000 hours of operation or maximum after a year;
– the second stage of filtration, as well as filters in air exhaust or recycling systems, must be changed after 4,000 hours of operation or maximum after 2 years;
– for the purposes of hygiene, the filter must be replaced in autumn, after the pollen and spore season.
If there are strict requirements in place, the filters can be replaced in spring after the seasons when the heating is kept on, to eliminate odours due to combustion.”