About Central Filtration Systems
Air cleaning systems can also be installed in the central heating or air-conditioning systems of a residence or in an HVAC system. These units are commonly referred to as "in-duct" units, although this term is actually a misnomer since they are not located in the distribution ductwork, but rather in unducted return air grilles or ducted return air plenums.
The term "central filtration system" will be used in this document. This type of unit provides building-wide air cleaning and, by continuously recirculating building air through the unit, can potentially clean the air throughout the entire air handling system, duct work and rooms. However, with these types of units, the HVAC fan must be in constant operation for air cleaning to occur since the airborne contaminants must be captured and carried back to the centralized filter for capture and retention. Thus, central filtration systems must be operated with the fan "on" for constant air movement through the HVAC system. |
