What is CFM and how to calculate it?
The fetched OmniCalculator page defines CFM as cubic feet per minute, a volume flow rate commonly used for fans and ventilation systems. For room ventilation, Omni uses:
airflow = floor area x ceiling height x ACH / 60
ACH = 60 x airflow / room volume
Room air change requirements from Omni
The fetched source page lists typical ACH ranges such as basements at 3-4, bedrooms at 5-6, bathrooms at 6-7, living rooms at 6-8, kitchens at 7-8, and restaurant kitchens at 14-60.
Sample calculation from the source page
Omni's worked example uses a 250 ft^2 home kitchen, 8 ft ceiling height, and 8 ACH. That gives 266.67 CFM, which is the default example loaded into this calculator.