Air changes per hour


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Air changes per hour

(ACH)
A metric of the air-tightness of a structure, often expressed as ACH50, which is the air changes per hour when the house is depressurized to50 pascals during a blower door test. The term ACHn or NACH refers to “natural” air changes per hour, meaning the rate of air leakage without blower door pressurization or depressurization. ACHn or NACH is used by many in the residential HVAC industry for system sizing calculations.
References in periodicals archive ?
8 shows the volume flow rate and air changes per hour necessary to drive the neutral pressure plane above the top floor in the building.
5 to 2 air changes per hour is highest for low-concentration exposures and decreases with increasing concentration of the aerosol exposure.
A lab's self-contained HVAC unit must have an increased number of air changes per hour, which means how often the room is completely replaced with fresh air from outside.
We have spent weeks with engineers calculating the number of air changes per hour required in various parts of the building.
Both the air exchange rate and ventilation air rate use air changes per hour as their units of measure.
The room should have at least six air changes per hour and should be maintained at negative pressure so that air flows from the halls into the room, preventing contaminated air from escaping.
The system is enclosed in a sealed room with 14 filtered air changes per hour.