Confined-space gas detection: catalytic bead vs. infrared technology

Responding is Dave Wagner, director, applications engineering and product knowledge, Industrial Scientific Corp., Pittsburgh.

A great deal of debate exists in industry today over the answer to this question. The discussions center on the pros and cons of using newer, low-power infrared technology versus the old standard catalytic bead technology for detecting combustible gases.

Low-power infrared technology brings a number of significant advantages to combustible gas detection. Unlike their catalytic bead counterparts, infrared sensors are not susceptible to damage from common poisons such as silicone and sulfur vapors. Silicone vapors, in particular, could be prevalent in confined space work and may increase detector maintenance costs because of rapid sensor poisoning.

Another advantage to using infrared technology is the ability to detect combustible gases in an oxygen-free environment, which spells trouble for a catalytic bead sensor. With lack of oxygen being the most common atmospheric hazard in confined space entry, it would seem to make sense that infrared sensors would be better suited for the job. Add the fact that low-power infrared sensors use far less energy from batteries than catalytic bead sensors – allowing for longer instrument run times – and it would seem to be a no-brainer that if you are going to enter a confined space, you should pick an instrument with an infrared sensor to do your atmospheric testing.

But hold the phone a minute before going out and picking up those infrared-based detectors. The catalytic bead sensor has been the “old guard” industry standard for a reason or two. The limitations of catalytic bead sensors have been well understood and dealt with for years.

Poisoning can be an issue for sure if you are not regularly testing and calibrating your sensors to identify it, and the lack of oxygen easily is dealt with if using a dilution tube. Long battery run times aren’t much of an advantage in confined space entry because entry permits rarely should be valid longer than a work shift anyway. The primary advantage of the catalytic bead sensor is that it is capable of being used to detect virtually any combustible gas or vapor if the particular sensor being used does not have a filter that reduces sensitivity to some heavier hydrocarbon vapors. Compare that with the fact that the infrared sensor is completely incapable of detecting hydrogen or acetylene – which can be common combustible gases found in confined spaces – along with several others that the infrared sensors will miss, and you would seem to have your answer.

If I am going to enter a confined space that might be holding a combustible gas that could explode and take my life, I am going to rely on a previously tested sensor that I know is capable of detecting whatever gas could be in the space. I am going to test my space with an instrument using a catalytic bead combustible gas sensor and leave the infrared sensors to applications for which they are much better suited.