Environmental Engineering Reference
In-Depth Information
chapter twelve
Air cleaning
Air cleaning is commonly used in industrial operations to reduce emissions
of particulate dusts as well as gaseous and vapor-phase contaminants to
the ambient atmosphere. It is also used as a contaminant control measure
in indoor environments. Air cleaning is used both generically and to control
specific contaminant problems. It is often used by individuals in an attempt
to reduce exposure to allergens and other suspected indoor air contami-
nants. It is rarely used as a mitigation measure to resolve problem building
complaints.
In most applications, air cleaning is a process in which airborne contam-
inants are removed from a moving airstream by some type of physical,
chemical, or physical-chemical process. Less commonly, air cleaning is
attempted by introducing charged ions into indoor spaces, or using oxidizing
substances such as ozone (O
) or passive systems such as plants.
Though air cleaning systems may be used generically to improve overall
cleanliness in indoor spaces and protect mechanical equipment in (1) heating,
cooling, and ventilation (HVAC) systems in mechanically ventilated build-
ings and (2) residential heating and cooling systems, air cleaners cannot, as
many lay individuals believe, be universally applied for the control of all
airborne contaminants. Most air cleaners have been designed to collect air-
borne particles, and thus cannot control gas/vapor-phase contaminants.
However, air cleaners can be designed to control specific gas/vapor-phase
substances or classes of substances, or a combination of particle and
gas/vapor-phase contaminants.
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I. Airborne particles and dusts
Most indoor spaces are sufficiently contaminated by airborne particles to
warrant at least a minimum level of air cleaning. Particles may be generated
indoors from a variety of activities and sources or enter indoor spaces from
