Instruments With Detector Tube Levels Of Accuracy Just Don't Cut It Anymore

The historical roots of toxic gas detection are far more rough-and-ready than precision analytical chemistry. After all, we're talking about canaries in coal mines and colorimetric detector tubes. Per the American Industrial Hygiene Association publication entitled Direct-Reading Colorimetric Indicator Manual (Second Edition, 1993):  The accuracy of detector tubes generally is considered to be ±25% of the reading.

While available instrumentation certainly improves on this—being based on calibrations using standards claiming ±2% accuracy—bad habits persist. In many cases, field calibration techniques are far inferior to those used by the instrument manufacturers themselves. And, in some instances, (hydrogen peroxide and peracetic acid, for example), commercial standards simply do not exist.

Interscan has developed its own calibration methods for these gases, which combine precision gas mixture generation methods with on-the-fly laboratory wet chemical analytics. In light of these processes, the company has audited and revised all of its calibration procedures, including those in which commercial standards are available.

"Developing these new calibration methods has given us a chance to also improve all of our protocols," said Grant McClure, Interscan's manager of special projects. "We have established enhanced techniques of pressure, temperature, and flow control; and invoke routine wet chemical testing, when appropriate."

The takeaway here is that the old, sloppy approaches to instrument calibration, which may have sufficed when regulatory levels were 50 or 100 parts-per-million, will fail badly now. Indeed, regulatory levels these days are more like 5 ppm, 1 ppm, or even lower.

Interscan Corporation is proud to be a leader in the "Real Analytics" movement in toxic gas detection, and will be issuing regular updates on how our enhanced techniques help our customers.