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Air changes per hour, abbreviated ACPH or ACH, or air change rate is the number of times that the total air volume in a room or space is completely removed and replaced in an hour. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each hour.
cubic centimetre of atmosphere; standard cubic centimetre: cc atm; scc ≡ 1 atm × 1 cm 3 = 0.101 325 J: cubic foot of atmosphere; standard cubic foot: cu ft atm; scf ≡ 1 atm × 1 ft 3 = 2.869 204 480 9344 × 10 3 J: cubic foot of natural gas: ≡ 1000 BTU IT = 1.055 055 852 62 × 10 6 J: cubic yard of atmosphere; standard cubic yard: cu yd ...
A normal cubic meter (Nm 3) is the metric expression of gas volume at standard conditions and it is usually (but not always) defined as being measured at 0 °C and 1 atmosphere of pressure. A standard cubic foot (scf) is the USA expression of gas volume at standard conditions and it is often ( but not always ) defined as being measured at 60 ...
References will be made to "actual" flow rate through a meter and "standard" or "base" flow rate through a meter with units such as acm/h (actual cubic meters per hour), sm 3 /sec (standard cubic meters per second), kscm/h (thousand standard cubic meters per hour), LFM (linear feet per minute), or MMSCFD (million standard cubic feet per day).
cubic metre: m3 m 3: US spelling: cubic meter one kilolitre 1.0 m 3 (35 cu ft) cubic centimetre: cm3 cm 3: US spelling: cubic centimeter one millilitre 1.0 cm 3 (0.061 cu in) cc cc cubic millimetre: mm3 mm 3: US spelling: cubic millimeter: 1.0 mm 3 (6.1 × 10 −5 cu in) non-SI metric: kilolitre: kl kl US spelling: kiloliter one cubic metre 1.0 ...
Actual cubic feet per minute (ACFM) is a unit of volumetric flow. It is commonly used by manufacturers of blowers and compressors. [1] This is the actual gas delivery with reference to inlet conditions, whereas cubic foot per minute (CFM) is an unqualified term and should only be used in general and never accepted as a specific definition without explanation.
Environmental agencies in the USA often use the terms "dscf" or "scfd" to denote a "standard" cubic foot of dry gas. Likewise, they often use the terms "dscm" or "scmd" to denote a "standard" cubic meter of gas. Since there is no universally accepted set of "standard" temperature and pressure, such usage can be and is very confusing.
This calculation seems off: "Ventilation rates are often expressed as a volume rate per person-minute (CFM per person, L/s per person)." So the numerator in the equation should have volume (Air changes per hour), but the denominator should have persons. The problem is the "D" in the formula. It says it's Occupant density (occupants/ft).