Air changes per hour (ACH) is calculated by...

Air changes per hour (ACH) is calculated by...

• A. Air Changes Per Hour (ACH)
• B. Lumen
• C. Illuminance
• D. IDLH

Answer: (A)

Air changes per hour shows how many times the entire air in a space is replaced in one hour. It’s found by relating the ventilation rate to the room’s volume. In customary units, use ACH = (Q × 60) / V, where Q is the supply air flow in cubic feet per minute and V is the room volume in cubic feet. In metric units, ACH = Q / V, with Q in cubic meters per hour and V in cubic meters. For example, with a room volume of 2,000 ft³ and a supply of 200 CFM, ACH = (200 × 60) / 2000 = 6 air changes per hour. This concept is separate from light-related terms like lumen or illuminance, and from the hazard designation IDLH.

Air changes per hour shows how many times the entire air in a space is replaced in one hour. It’s found by relating the ventilation rate to the room’s volume. In customary units, use ACH = (Q × 60) / V, where Q is the supply air flow in cubic feet per minute and V is the room volume in cubic feet. In metric units, ACH = Q / V, with Q in cubic meters per hour and V in cubic meters. For example, with a room volume of 2,000 ft³ and a supply of 200 CFM, ACH = (200 × 60) / 2000 = 6 air changes per hour. This concept is separate from light-related terms like lumen or illuminance, and from the hazard designation IDLH.