Glossary
Air Changes per Hour — Glossary
How many times a room's air is replaced per hour — the ventilation metric that sets odor dilution.
Air changes per hour (ACH) measures ventilation — an ACH of 1 means the room’s air is replaced once hourly; 5 means five times. Higher ACH means faster odor dilution.
It is the measurable difference between a stuffy room and a fresh one — the same odor source reads completely differently at different ACH.