The calculation methods for determining CFM (Cubic Feet per Minute) in HVAC systems. It presents three primary methods: 1) Based on room size, where CFM is calculated by multiplying room volume (Length × Width × Height) by air changes per hour (ACH) and dividing by 60; 2) From air velocity, where CFM is determined by multiplying the duct area (in square feet) by air velocity (in feet per minute); and 3) Using HVAC equipment tonnage, where CFM is calculated by multiplying the number of tons of th