Aspects Related to the Quality of Extract or Exhaust Air

In many of these aspects, the Extract Air Classification, summarized in Table 9.22, is a useful tool to assist in system design. Applications of these classifications are described in Annex A of prEN 13779. 

Categories for exhaust air (EHA) are also defined in prEN 13779. Normally the EHA category for air to be discharged outdoors is the same as ETA, but if the system includes reliable and monitored cleaning equipment, the category can be one lower. With these provisions, air from industrial processes with very high pollution level, in category ETA 4 can be cleaned to EHA 3 levels. 

ETA 1 Air of the same qualit as outdoors with respect tr humidity. From rooms with pollutant sources from humans and building mtiterinl. Offices, storage rooms, public service places. No major pollution sources, including smok ing. 

ETA 2 Air from occupied spaces that have impurities in excess of F.TA 1. Smoking lounges, eating areas. 

ETA 3 Spaces in which moisture, chemical processes, etc. substantially lewder air quality. 7 oilecs, kitchens, garages, tunnels, car parks, solvent areas, laboratories. 

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