25 October 2004
A device designed for the purpose of removing atmospheric
airborne impurities such as dusts, gases, vapors, fumes, and
smoke. (Air cleaners include air washers, air filters,
electrostatic precipitators and charcoal filters.)
An air cleaning device to remove light particulate loadings
from normal atmospheric air before introduction into the
building. Usual range: loadings up to 0.0069 g/m3 (3 grains
per thousand ft3). Note: Atmospheric air in heavy industrial
areas and in-plant air in many collectors are then indicated
for proper air cleaning.
Dry air at 70 degrees F, 21.11 degrees C, and 29.92 in. Hg
barometer. This is substantially equivalent to 0.075 pounds
per cubic feet (lb/ft3). Specific heat of dry air = 0.24 Btu/lb-F
Aspect ratio (AR)
Ratio of the width to the length; AR = W/L.
Air velocity at any point in front of the hood or at the hood
opening necessary to overcome opposing air currents and to
capture the contaminated air at that point by causing it to
flow into the hood.
Small solid particles created by the breaking up of larger
particles by processes crushing, grinding, frilling, explosions,
etc. Dust particles already in existence in a mixture of
materials may escape into the air through such operations
as shoveling, conveying, screening, and sweeping.
Air cleaning device to remove heavy particulate loadings
from exhaust systems before discharge to outdoors. Usual
range: loadings 0.003 grains per cubic foot and higher.
This term applies to the fan's performance abilities. The
required fan class is determined according to the operating
point of the ventilation system. AMCA 99-2408 provides a
set of five minimum performance limit standards (Class I
through V) which manufactures use to apply the correct
class to their fans.