Air sample volume calculator
Flow rate × duration gives the liters of air drawn through a spore-trap cassette. Match indoor and outdoor volumes so the only difference your lab reads is the air itself.
Calibrated flow rate of your air-sampling pump.
How long the cassette ran.
How air-sample volume works
A spore-trap result is only as good as the volume behind it. The sampled volume is simply the pump's calibrated flow rate (liters/minute) multiplied by the run time (minutes); dividing by 1,000 converts liters to cubic meters, the unit the lab reports counts in (spores/m³). A common protocol runs roughly 15 L/min for about 5 minutes — near 75 liters — which many labs treat as a practical floor for a representative residential air sample. There is no standard-published minimum volume; this is a guidance flag, not a pass/fail.
The volume that matters most is the match between your indoor and outdoor samples. An air result is read against a same-day outdoor control, so if the indoor cassette ran 5 minutes and the outdoor ran 3, you are comparing apples to oranges. Run identical flow and duration on both — see air pump calibration for why a calibrated, matched volume is the foundation of the indoor:outdoor comparison.
Related reading
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