About OdorTest

Odour is one of the harder things in environmental work to pin down. It is a sensory response, not a straightforward chemical reading, so the numbers that describe it — odour units, dilution factors, emission rates, separation distances — come with their own vocabulary and their own arithmetic. OdorTest is a small, independent site that puts the common calculations behind odour measurement in one place, so you can move between them without hunting for the formula each time.

What the tools do and where the numbers come from

Every calculator here is built on the framework of dynamic olfactometry described in the EN 13725 standard, where a sample is diluted with clean air until a trained panel can only just detect it. The Odor Concentration Calculator turns that dilution-to-threshold ratio into an odour concentration in European odour units per cubic metre — the quantity the whole field is built around. The Dilution Ratio Calculator works out an olfactometer’s dilution factor from its clean-air and sample flows, and the concentration that leaves for the panel’s nose. The Odor Emission Rate Calculator multiplies a concentration by a source’s volumetric air flow to give the emission rate in odour units per second, converting between cubic metres per second, minute, and hour along the way. The Detection Threshold Calculator reduces a panel’s individual threshold estimates to a single group threshold using the geometric mean, because olfactory sensitivity is log-normally distributed. The Ventilation Dilution Calculator converts a room volume and air-change rate into clean-air flow, a steady-state concentration for a given source, and the time to purge a space. And the Odor Impact Distance Estimator gives a screening-level separation distance from an emission rate, an acceptance criterion, and a simple dispersion factor.

The formulas are the standard ones — a dilution factor is total flow over sample flow, an emission rate is concentration times flow, a group threshold is the antilog of the mean of the logs. What the tools add is the unit handling and the plain-language explanation, so the result and the reasoning behind it sit on the same page.

What this is, and what it isn’t

OdorTest is an independent, advertising-supported site. The ads are how the calculators stay free with no account or sign-up. It is not a testing laboratory, it is not accredited, and it is not affiliated with any standards body, instrument maker, or regulator it mentions. The calculators produce screening estimates from the figures you enter; they are not a substitute for accredited EN 13725 olfactometry, validated dispersion modelling, or professional environmental and regulatory advice. For a defensible odour result — the kind that stands up in a permit application or a complaint investigation — you need a qualified laboratory and practitioner, calibrated equipment, and a screened panel, none of which a web page can replace.

Alongside the tools, the blog and learn section explain the concepts the calculators rest on, and the museum is a browsable illustrated collection drawn entirely from Wikipedia and Wikimedia Commons. If a tool gives a result that looks wrong, or there is a calculator you wish existed here, the contact page is the place to say so.