Page 454 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

14.3 IAQ Control by Ventilation/Dilution 435

14.3 IAQ Control by Ventilation/Dilution

Indoor air quality (IAQ) can be effectively controlled by HVAC systems. The
acronym HVAC stands for heating, ventilation and air conditioning. A HVAC
system provides treated outdoor air to the indoor environment and deliver it to the
point of interest through ducts. As shown in Fig. 14.1, outdoor air enters the system
through the air intake followed immediately the air cleaning devices, most likely a
filter. As needed, air can be heated or cooled depending on the weather condition.
Moisture can be added or removed as well. The air after filtration and conditioning
is then distributed to multiple points in the building through supply air duct. After
mixing within the rooms, air pollutants will be taken out of the room and become
return air. Meanwhile, the temperature and humidity of the indoor air are adjusted
to a comfort level. A portion of the return air, after treatment, is merged with the
intake air in order to save energy. The rest will be discharged to the atmosphere
through the exhaust.

14.3.1 Minimum Ventilation Rate

Ventilation controls the indoor air quality by bringing fresh air into an indoor
environment to supply or reduce the heat and moisture and to dilute gaseous and

Fig. 14.1 HVAC system with internal air circulation and cleaning