The acronym ACH stands for which of the following?

The acronym ACH stands for which of the following?

• A. Air Circulation Per Hour
• B. Air Changes Per Hour
• C. Ambient Change in Humidity
• D. Average Chemical Hazard

Answer: (B)

Air changes per hour describes how many times the air in a space is replaced each hour. The acronym ACH is exactly that: the rate at which ventilation cleans the air by diluting and removing contaminants. It’s calculated by dividing the ventilation rate by the room volume: ACH = Q / V, where Q is the supply air flow in cubic meters per hour and V is the room volume in cubic meters. This metric helps IH professionals assess whether a space has enough ventilation to protect occupants and control contaminants. For example, a 150 m^3 room with a ventilation supply of 450 m^3/h achieves 3 air changes per hour, meaning the room’s air is replaced about three times each hour. The other options aren’t standard ventilation terms: air circulation per hour isn’t a recognized metric; ambient change in humidity refers to humidity shifts, not air replacement; and average chemical hazard isn’t a ventilation metric.

Air changes per hour describes how many times the air in a space is replaced each hour. The acronym ACH is exactly that: the rate at which ventilation cleans the air by diluting and removing contaminants. It’s calculated by dividing the ventilation rate by the room volume: ACH = Q / V, where Q is the supply air flow in cubic meters per hour and V is the room volume in cubic meters. This metric helps IH professionals assess whether a space has enough ventilation to protect occupants and control contaminants. For example, a 150 m^3 room with a ventilation supply of 450 m^3/h achieves 3 air changes per hour, meaning the room’s air is replaced about three times each hour. The other options aren’t standard ventilation terms: air circulation per hour isn’t a recognized metric; ambient change in humidity refers to humidity shifts, not air replacement; and average chemical hazard isn’t a ventilation metric.