Gas exposure limits

Responding is David D. Wagner, director of product knowledge and iNet product manager, Industrial Scientific Corp., Oakdale, PA.

Awareness and concern about exposing workers to toxic and carcinogenic gases and vapors is much greater than it has been in the past – and rightly so. Previously, more focus was placed on gas exposures that may be considered immediately dangerous to life and health. Today, much more thought is given to the effects of gas exposure later in life.

In recent years, the American Conference of Governmental Industrial Hygienists has reduced the threshold limit value recommendations of common toxic industrial gases such as hydrogen sulfide, sulfur dioxide and nitrogen dioxide. The group has done so based on the determined health effects of the various gases – but also has done so with a blatant disregard for whether the commonly used detection technologies are capable of adequately sensing the gases at the lower levels.

Lower tolerance for gases doesn’t stop with toxic gases. Although working in areas where combustible gas levels may be found at 20 percent of the lower explosive limit (or even higher) may at one time have been considered acceptable, many companies today are moving toward a zero-tolerance LEL policy. Maintaining conditions in areas where combustible gases are commonly known to exist and environmental conditions can be considered extreme at a zero percent LEL state is certainly taxing combustible gas detection technologies with requirements for accuracy and stability far greater than anything that has been seen in the past.

Dealing with lower gas exposure limits, whether toxic or combustible, has created issues for both industrial safety professionals and gas detection equipment manufacturers. While plant safety and operations managers fight to control gas emissions and exposure levels, gas detection equipment manufacturers struggle to build and supply detectors capable of providing consistent and accurate information at the lower gas levels. For example, the options today for sensors that can detect SO₂ or NO₂ at the American Conference of Governmental Industrial Hygienists-recommended TLV levels are extremely limited.

Likewise, building combustible gas sensors that consistently maintain stable baseline zero readings in extreme and varying conditions of temperature and humidity is nothing less than daunting.

The challenge is great, but no one should expect the current trends toward lower gas exposure limits to reverse themselves, nor should they want them to. To meet the challenge, gas detection equipment manufacturers will have to dedicate themselves to researching new and improved sensing technologies capable of providing higher performance at lower gas levels. Positive results will not come overnight, but the coming years should bring technologies that put the detection equipment ahead of the curve.

Ultimately, ending injury and death due to gas exposure and gas incidents will require eliminating gas hazards. Until that can happen, the world will have to rely on quality gas detection equipment. Can today’s technology keep up with the current trends in lower exposure limits? No. But give it a bit of time and I believe it will exceed our needs and expectations.

Editor's note: This article represents the independent views of the author and should not be construed as a National Safety Council endorsement.