Air Sampling Volume Calculator

This calculator computes the total air volume collected during an industrial hygiene personal or area sampling run, then converts an analytical laboratory result into an airborne concentration — the two calculations that turn a raw sample into an exposure number. The uncorrected volume is simply the calibrated pump flow rate multiplied by sampling duration; a full 8-hour shift at a typical low-flow pump setting is the classic time-weighted-average sampling scenario, entered here as the 480-minute default. Because gas volume depends on temperature and pressure, the calculator also applies a standard-conditions correction — adjusting the measured volume to a reference temperature and pressure (25 °C, 760 mmHg, the conventions commonly used in industrial hygiene analytical methods) using the combined gas law, so that a sample collected on a hot day or at altitude is put on the same footing as one collected at standard conditions before it's used to compute a concentration. Once a laboratory reports the mass of analyte recovered from the sampling medium, dividing that mass by the actual (uncorrected) sample volume yields the airborne concentration in mg per cubic meter — standard OSHA/NIOSH practice reports exposure concentration at real field conditions, since a PEL or TLV describes the concentration a worker actually breathed, not a temperature/pressure-normalized figure — which the calculator can further convert to parts per million for gases and vapors using the molar volume relationship (valid at 25 °C and 1 atmosphere) and the substance's molecular weight.

The STP-corrected volume is reported separately as a gas-metering/pump-verification figure, not as the concentration denominator. What this doesn't capture: any specific occupational exposure limit — permissible exposure limits (PELs), threshold limit values (TLVs), and other regulatory or advisory limits are substance-specific, vary by regulatory body and jurisdiction, and are updated periodically, so this calculator computes a concentration only; comparing that concentration against the correct current limit for the specific substance sampled requires consulting the applicable regulation (such as 29 CFR 1910.1000 in the US) or current ACGIH TLV documentation directly. It also assumes the pump was properly calibrated before and after sampling and that the sampling medium efficiently captured the analyte — neither of which this calculator can verify.