Originally Posted By: Jim Acord
This post was automatically imported from our archived forum.
I have noticed that there are several discussions related to combustible gas indicators (CGIs) and carbon monoxide (CO) monitors. There are several misconceptions that need to be clarified.
First, who am I? I am considering become a certified home inspector in the State of Indiana. Over the last twenty (20) years, I have either worked for a major gas utility company or one of its subsidiaries. The last subsidiary that I worked for supplied materials and services to it?s parent energy companies. One of those services was the repair and calibration of combustible gas indicators (CGIs), carbon monoxide (CO) monitors, confined space monitors, and oxygen depletion sensors. I have worked on all of the aforementioned units. I have performed literally tens of thousands of calibrations. I authorized by various manufacturers to work on their equipment ? in some cases, I am the only person that is allowed to perform this work outside of their on staff. My input has been sought on the design and operation of various instruments, from various manufacturers. I am a Senior Member in the Instrument Society of America. I am an electrical engineer but I am not a salesman: if you ask me my opinion on an instrument, you get a straight answer.
With regards to gas detectors, currently, most of the discussions on these forums relate to solid-state semiconductor technology. The J and N Enterprise?s Gas-Trac, the J and N Enterprise?s Sensit, the Bacharach Leakator 10, and UEi? Combustible Gas Leak Detector, are examples of this. These instruments are GENERAL gas detectors, i.e. they do not distinguish what type of gas is present nor do they quantify the gas. You don?t know what the gas is nor do you know how bad the leak is! They can be sent into alarm simply by breathing on them. Strong cologne or perfume will set them off.
Does this make them unacceptable or unuseable? No! They indicate the presence of _something_, you just don?t know what.
As for quantifying a gas or properly identifying it, the two most common type of sensors ? right now ? are pellister and solid state sensor (but not a semiconductor). These solid-state sensors are gas-specific and are only cross-sensitive to a handful of similar gases. For example, a methane-calibrated instrument will generally detect propane, butane, pentane, and methane.