Calculate required fresh air (CFM) for proper ventilation based on occupancy and ASHRAE standards.
Fresh Air Requirement is the volume of outdoor air required to properly ventilate a space according to occupancy and ASHRAE standards. It maintains indoor air quality and comfort for all occupants.
Formula:
Total Fresh Air CFM = (Number of Occupants × CFM per Person) + (Room Area × CFM per ft²)
Room: 20 occupants, 500 ft², CFM per person = 20, Area CFM = 0.12:
People contribution = 20 × 20 = 400 CFM
Area contribution = 500 × 0.12 = 60 CFM
Total Fresh Air = 400 + 60 = 460 CFM
✅ This is the fresh air required to ventilate the room properly.
| Space Type | CFM per Person |
|---|---|
| Office | 20 |
| Classroom | 15 – 20 |
| Conference Room | 15 – 20 |
| Restaurant | 20 – 30 |
| Hospital Room | 25 – 30 |
ASHRAE provides guidelines to maintain adequate ventilation, indoor air quality, and comfort while ensuring energy efficiency.
Insufficient fresh air can lead to high CO2 levels, odors, discomfort, and potential health risks for occupants.
Yes, CFM per person can vary based on activity level, occupancy density, and type of space. Use ASHRAE tables as reference.