Odorant Concentration vs. Odor Intensity: What's the Difference?
- 2 days ago
- 2 min read
If you've spent any time researching how to verify odorant levels in a natural gas system, you've probably run into two very different answers to what sounds like the same question. One approach measures odor intensity: a person, or an instrument standing in for a person, judges whether gas is detectable at a given dilution. The other measures odorant concentration directly, in parts per million, using a sensor rather than a judgment call. These aren't competing brands of the same tool. They're two different methods, and knowing which one you actually need matters.
Odor Intensity Testing: Measuring Detectability
Odor intensity instruments are built around a core idea: dilute a gas sample to a known ratio and determine, at that dilution, whether the odor is still detectable. Traditionally this was done by a trained person sniffing a sample port directly. Modern versions of this approach have added GNSS location logging, digital record-keeping, and automated dilution control, but the underlying test is still built around detectability at a threshold, not a direct chemical reading. This is a long-established, industry-standard approach to demonstrating compliance with 49 CFR 192.625's detectability requirement, and it remains a valid, widely used method.
Concentration Measurement: Reading the Number Directly
An electrochemical odorant analyzer works differently. Instead of asking whether gas is detectable at a diluted ratio, it reads the actual odorant concentration in the gas stream, in parts per million, for a specific odorant like TBM or THT. There's no threshold judgment involved. The instrument reports a number, and that number can be logged, trended over time, and compared directly against a target concentration.
Where This Distinction Actually Matters
Troubleshooting odor fade: a concentration reading tells you how far below target you are, not just that you're below detectable. That's a meaningfully different diagnostic starting point.
Verifying pickling progress: tracking concentration across multiple cycles shows a trend line, not just a pass or fail at the end.
Documenting for a specific odorant blend: a concentration reading is tied to the specific chemical you're measuring, which matters when a system uses a particular TBM or THT blend rather than a generic mixture.
Comparing results across sites or over time: a number in ppm is directly comparable in a way a detectability threshold isn't.
What Our Analyzer Actually Is, and Isn't
Our portable odorant analyzer uses an electrochemical sensor we specified for this exact application, field measurement of TBM and THT concentration during pickling, commissioning, and routine verification work, and we wrote the field procedure and calibration workflow around it. We didn't take a general-purpose gas detector and call it done. The sensor selection and the procedure are built specifically for odorant work, which is different from adapting an off-the-shelf instrument designed for something else.
Choosing the Right Tool for the Job
Neither approach is universally better, they answer different questions. If your compliance program is built around detectability testing, an intensity instrument is the established tool. If you need a direct, trackable concentration number, for troubleshooting odor fade, verifying pickling progress, or documenting a specific odorant blend, a concentration analyzer is the more useful instrument. For background on the regulation both approaches are ultimately serving, see our breakdown of
49 CFR 192.625, and for general odorization terminology, our Comprehensive Odorization Glossary.
