Ventilation rate calculator
Ventilation is sized either by air changes per hour or by litres per second per person. Carbon dioxide is the usual proxy for whether it is enough.
L/s
per hour
ppm
Ventilation rate needed
62.5L/s
- In cubic metres per hour
- 225.0
- In cubic feet per minute
- 132.4
- Air changes per hour
- 3.000
- Room volume
- 75.00
- Steady-state CO2
- 919 ppm Acceptable
- Rate from the per-person requirement
- 60.0 L/s
Show the working
- Floor area = 30
- Ceiling height = 2.5
- Occupants = 6
- Air per person = 10
- Or a target air change rate = 3
- Outdoor CO2 = 420
- Room volume = 30 * 2.5 = 75
- Rate from the per-person requirement = 6 * 10 = 60
- flow_ach = 75 * 3 / 3.6 = 62.5
- Ventilation rate needed = max(60, 62.5) = 62.5
- Air changes per hour = 75 > 0 ? 62.5 * 3.6 / 75 : 0 = 3
- In cubic metres per hour = 62.5 * 3.6 = 225
- In cubic feet per minute = 225 * 0.5885777777777777 = 132.43
- Steady-state CO2 = 62.5 > 0 ? 420 + 6 * 0.0000052 / (62.5/1000) * 1e6 : 0 = 919.2
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- flow from air changes = volume x ACH / 3.6, in litres per second
- steady-state CO2 = outdoor CO2 + generation rate / ventilation rate
- a resting adult exhales about 0.0052 litres of CO2 per second
CO2 is not itself the hazard at these levels; it is a marker for how much exhaled air you are re-breathing.