Performance requirements for ventilation and air-conditioning systems.
The standard is applied to the design and creation of ventilation and air-conditioning systems for non-residential buildings used for human occupancy, except for applications in industrial processes. It defines the main relevant parameters for such systems and does not cover buildings with natural ventilation.
The standard, currently under revision, focuses on attaining a comfortable and healthy environment inside buildings, using ventilation systems with affordable running costs. It specifies the required performance of the filtering system in a ventilation system to achieve good quality levels for indoor air (IAQ) starting from the quality of outdoor air. Outdoor air is classified on 3 levels, from ODA1 where the air is clean, except for temporary pollution (such as pollen), to ODA 3 where the air contains a high concentration of gas and particles.
Given the “side effects” of these substances, the World Health Organization recommends not exceeding the limit concentration values for the following indoor pollutants:
|Pollutant Limit concentration in the air||Exposure time||Limit concentration in the air|
|Total PM||1 year||100||–|
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:
|Category||Geographical area||CO mg/m3||CO2 ppm||SO2 μg/m3||NO2 μg/m3||Tot. PM mg/m3||PM10 μg/m3|
|ODA1||Rural area||<1||350||< 5||5 ÷ 35||< 0.1||< 20|
|ODA2||Suburban area (or small town)||1 ÷ 3||375||5 ÷ 15||15 ÷ 40||0.1 ÷ 0.3||10 ÷ 30|
|ODA3||Polluted city centre||2 ÷ 6||400||10 ÷ 50||30 ÷ 80||0.2 ÷ 1.0||20÷ 50|
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:
|Category||CO2 level above the one in ODA||Amount of outdoor air per-head [m3/h/person]
Areas where smoking is not allowed
|Typical range [ppm]||Default value [ppm]||Typical range [ppm]||Default value [ppm]|
|IDA 1||≤ 400||350||54||72|
|IDA 2||400 ÷ 600||500||36 ÷54||45|
|IDA 3||600 ÷ 1000||800||22 ÷36||29|
|IDA 4||> 1000||1200||< 22||18|
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.”
|Outdoor Air||IAQ (indoor air quality)|
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