September 2009

It's Dark in Here and It Smells Funny Too... Gas Monitors and
Their Importance in a Confined Space
by a Senior Inspector, Infrastructure Engineers, Inc.

There are several different types of gas monitors; some that are waterproof, some that are rechargeable, and some that check for additional hazards in the air you breathe. They all perform a common goal, which is keeping you alive to perform the next inspection and to assure that you get home safely.

A gas monitor is a highly sensitive device that must be carefully handled and treated with respect. It should not be subjected to impacts or jolts. In order to ensure that it is working properly, a qualified individual should calibrate it at least every six months against a known percentage of gas. Some of the parts inside of it, especially the sensors, have a shelf life and do expire. Keep the maintenance current and save the documentation, calibration certificates, and even the manufacturer's warranty (the warranty has paid for itself a few times with the experiences that I have had). Read the instruction manual on the proper use. Most importantly, use it!

For our specialty line of work (bridge inspections), our routine usage of gas monitors include culvert inspections, some of which are as long as 850 feet. Trust me, when you're more than 50 feet in, can't see daylight after turning a corner, and there is only one way in or out, you want to be assured that the air is pure. We also use gas monitors for lengthy enclosed box girders that are required to be inspected inside and out due to the fracture critical details of the structure.

We have had false alarms with our gas monitors during inspections. We had to stop what we were doing and proceed to the nearest exit due to a sensor being bad. We have had times where our vendor would hand-deliver a replacement to us just to keep us on schedule. I have had to stop what I was doing and bring my monitor out as a spare to another inspection team in our firm because theirs stopped working. Each time, we have taken the alarm seriously, regrouped, assessed the nature of the alarm and either resumed where we left off, or saved the inspection for another day. A false alarm is better than an alarm that you can't respond to or protect yourself from due to the quick onset of unconsciousness and potentially, death.

The gas monitor can detect carbon monoxide - the odorless, colorless killer - well before you know that it exists in the air that you're breathing. It can detect the danger up ahead, from rotting vegetation or animal carcass that is giving off by-product, hydrogen sulfide, which is extremely toxic, both from acute and chronic exposure. Lastly, it may detect a hazardous atmosphere, such as supersaturated air with gas, vapor, fine mist, or an airborne combustible dust that exceeds a flammable limit.

So when your gas monitor goes into an alarm mode, it may be telling you that the small dose of the funny smell up ahead could be danger... stay away as if your life depended on it. Your life does depend on your gas monitor. Don't be another statistic on the evening news. Use it, calibrate it, maintain it, live... repeat.