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GACT (GENERALLY AVAILABLE CONTROL TECHNOLOGY): Methods, practices and techniques which are commercially available and appropriate considering economic impacts and the technical capabilities of the firms to operate and maintain the emissions control systems. Under Title III of the CAAA, EPA will establish either GACT or MACT standards for each source of HAPs.

GAS: Not a liquid or a solid. A state of matter with the ability to diffuse readily into other gases and tends to expand indefinitely.

GASES: Normally formless fluids which occupy the space of its enclosure and which can be changed to a liquid or solid state only by the combined effect of increased pressure and decreased temperature. Gasses diffuse.

GAS FLOW RATE, CUBIC FEET PER MINUTE (CFM): The volume of process gas at any point of the plant exhaust system measured in terms of minutes. There are several units of measurement:

ACFM: The actual gas volumetric flow rate (Actual Cubic Feet per Minute).

SCFM: The gas volumetric flow rate, corrected to 70° F (standard temperature) and standard pressure (1atm) by calculation (Standard Cubic Feet per Minute).

DSCFM: The 70°F (standard temperature) and standard pressure (1atm) and without volume of steam or water vapor contained in the exhaust gas (Dry Standard Cubic Feet per Minute).

GASOLINE VOLATILITY: The property of gasoline whereby it evaporates into a vapor. Gasoline volatility is measured in pounds per square inch (psi), with a higher number reflecting more gasoline evaporation. Gasoline vapor is a VOC (Volatile Organic Compound).

GAUGE (GAGE): Metal manufacturers’ standard measure of thickness for sheet stock; some examples for steel are:
Thickness Weight of Steel
Gauge (inches) (lbs/ft)
7 .1793 7.50
10 .1345 5.625
12 .1046 4.375
14 .0747 3.125
16 .0598 2.50

GAUGE PRESSURE: The pressure differential between atmospheric and that measured in the system.

GRAIN: A dust weight unit commonly used in air pollution control. Equal to one seven thousandth of a pound. One grain = 1 lb or 1 lb = 7,000 gr 7,000

GRAIN LOADING: The rate at which particles are emitted from a pollution source. Measurement is made by the number of grains per cubic foot of gas emitted.