Absorption:The process by which a liquid or a gas taken into the
intersticies of a porous substance and held there.
Activated carbon: Form of carbon capable of removing certain gases from the air.
Activated charcoal: See activated carbon.
Adsorbent: An absorber. That upon which adsorption takes place. it is the material to which a gas molecule is attached and retained.
Adsorption: The process by which gases adhere to solid surfaces. The strength of the bond depends on the van der Waal forces between the gas and the solid.
Adsorption Isotherm: A measurement of adsorption determined at a constant temperature by varying the amount of adsorbent used or the concentration of the adsorbate in contact with the carbon.
Aerosol: An assemblage of small particles, solid or liquid, suspended in air. The diameter of the particles may vary from 100 microns down to 0.01 microns. Examples: dust, smoke, fog.
Aerosol Photometer: A light-scattering mass concentrating indicator.
Aerosol Spectrometer: A device for measuring particle size and distribution in air.
AFTL Air Filter Testing Laboratory. This is an independant laboratory capable of testing filters by several standard test methods, and developing special test programs which may be required by client.
Agglomeration: The formation of a larger airborne particle by the collision of two or more smaller particles. Agglomeration takes place when the attractive forces between the particles is greater than the kinetic energy of collision.
AHAM: Association of Home Appliance Manufacturers.
Air The mixture of gases which make up the atmosphere. Air is composed of 78% nitrogen and 21% oxygen. The balance consists of smaller amounts of gases which vary with the locationin which the air is sampled.
Air Change: A measure of the amount of air moving into and out of a space because of leakage or mechanical ventilation. One air change is a volumetric flow of air equal to the cubic content of the space. Example: If a space has a cubic content of 10,000 cubic feet and the ventilation rate is 1000 cfm, 0.1 (1000/10,000) air change is occuring every minute, or 6 (60x0.1) air change are occuring per.
Air Cleaner: A device used for the removal of particulate or gaseous impurities from the air.
Air Conditioning: The process in which the physical condition of air within a space is maintained in a desired condition by controlling simultaneously its temperature, humidity, cleanliness and motion.
Air Diffuser: An air distribution outlet designed to direct airflow into desired patterns.
Air Filter: A device for removing particulate material from an airstream .
Air Resistance: See pressure drop and static pressure.
Alkali Any substance which in water solution is bitter and is irritating or caustic to the skin and mucous membranes, turns litmus blue and has a pH value greater than 7.0.
Ambient Air: Air which surrounds the occupant ot process in space.
Apparent Density: Weight of activated carbon per unit volume. Example: pounds per cubic foot.
Arrestance: A measure of the ability of an air filtration device to remove synthetic dust from the air. ASHRAE arrestance is a measure of the ability of a device to remove ASHRAE dust from test air.
ASHRAE American Society of heating, Refrigerating and Air-Conditioning Engineers.
Atmospheric Pressure: The pressure exerted upon the earth's surface by
the weight the atmosphere above it.