Ventilation Rate Chart
Minimum outdoor-air ventilation rates by occupancy per ASHRAE Standard 62.1, the Ventilation Rate Procedure. Each rate has two parts — a per-person component (Rp) and a per-area component (Ra) — and you add them: outdoor air equals Rp times the number of people plus Ra times the floor area. These are code minimums for acceptable indoor air quality.
ASHRAE 62.1 outdoor air rates
| Occupancy | Rp (cfm/person) | Ra (cfm/ft²) |
|---|---|---|
| Office space | 5 | 0.06 |
| Conference / meeting room | 5 | 0.06 |
| Classroom (age 9+) | 10 | 0.12 |
| Retail sales | 7.5 | 0.12 |
| Restaurant dining room | 7.5 | 0.18 |
| Hotel / dormitory bedroom | 5 | 0.06 |
| Health club / aerobics room | 20 | 0.06 |
| Corridors | — | 0.06 |
Two components, always added
The reason 62.1 splits the rate is that a space has two independent pollution sources. People generate CO₂, odors, and moisture — that scales with occupancy, so it is the Rp per-person term. The building itself off-gasses from finishes, furniture, and equipment — that scales with floor area, so it is the Ra per-area term. You always add both: a full conference room is dominated by its people, while an open lobby is dominated by its area. Divide the sum by the air-distribution effectiveness (how well the supply air actually reaches the breathing zone) to get the outdoor air the zone needs.
These are minimums for acceptable air quality, separate from the airflow needed to carry the heating or cooling load — the system moves far more total air than the outdoor-air minimum. For spaces sized by air changes instead, and for the healthcare rooms 62.1 excludes, see the air changes per hour chart, and turn the rate into airflow with the CFM calculator.
Common questions
How much outdoor air does ASHRAE 62.1 require?
62.1 uses a two-part rate: outdoor air = (people component) + (area component), or Vbz = Rp × people + Ra × floor area. For an office that is 5 cfm/person plus 0.06 cfm/sqft; a classroom is 10 cfm/person plus 0.12 cfm/sqft. Both components always apply — you add the per-person and per-area amounts together, then divide by the air-distribution effectiveness to get the zone outdoor airflow.
What are Rp and Ra?
Rp is the outdoor airflow required per person (cfm/person), covering the pollutants people generate. Ra is the outdoor airflow required per unit floor area (cfm/sqft), covering the pollutants the building and its furnishings give off. A densely occupied room is people-dominated; a sparsely occupied large space is area-dominated.
Does 62.1 cover hospitals?
No — health-care spaces like patient rooms and operating rooms are not in ASHRAE 62.1. The standard explicitly defers them to ASHRAE Standard 170, which sets them as air-change-per-hour minimums rather than cfm/person + cfm/sqft. Use the air changes per hour chart for those.
RUN THE NUMBERS
Run your whole job on the same numbers
These NORDIX tools are a taste of the full platform — bid pipeline, estimating, and job costing that carry your numbers from the first bid to the final invoice. Our team sets it up for your shop and walks you through your next real job.
Request access →