Air at a temperature of 68 °F, a pressure of 14.70 psia and a relative humidity of 36 per cent (0.0750 density) (as per A.S.M.E. however in the gas industry the temperature of standard air is usually given as 60 °F. ( Unless specifically stated otherwise) ( 060)
Air weighing 0.7488 pound per cubic foot, which is air at 68oF dry bulb and 50% relative humidity at a barometric pressure of 29.92 in. Hg.
Dry air weighing 0.075 lb per cu ft at sea level (29.92" Barometric Pressure) and 70 °F.
Air at 50% relative humidity, with a temperature of 21ºC (69.8ºF) and pressure of 760 mm Hg (29.92 in Hg.).
Air weighing 0.075 lb/ft3 [1.2 kg/m3] which approximates dry air at 70º F [21º C] and at a barometric pressure of 29.92 inches of Hg [101.3 kPa
Standard cubic foot Standard pressure and temperature (SPT)
The Compressed Air & Gas Institute and PNEUROP have adopted the definition used in ISO standards. This is air at 14.5 psia (1 bar); 68F (20C) and dry (0% relative humidity).
Air at 50% relative humidity 70oF and 29.92 in. Hg (21o and 760mm Hg). These conditions are chosen in recognition of the data which has been accumulated on air-handling equipment. They are sufficiently near the 25oC and 760mm Hg commonly used for indoor air contamination work that no conversion or correction ordinarily need be applied.
Air with a weight of 0.075 pounds per cubic foot with an equivalent density of dry air at a temperature of 86 degrees Fahrenheit and standard barometric pressure of 29.92 inches of mercury.