It is a well known and heavily publicized fact that carbon monoxide is a dangerous gas even at low exposure levels. While measurement solutions for residential applications are fairly simple, industrial and commercial applications require a much more sophisticated instrument. Problems with accuracy of many measurement devices arise due to zero instability and cross sensitivity to other gasses on sensors especially in industrial situations where temperature changes and presence of other process gasses are an ongoing part of everyday life. Upper exposure limits for CO in work place are normally set to provide alarms or warnings at 25-50ppm, sensor inaccuracies often cause alarms to be triggered when in fact no actual carbon monoxide danger exists.
When higher levels of CO are present, proper safety procedure calls for halt of production and evacuation of all personnel from area until levels can be verified, reduced and source identified. These precautions taken against this potentially deadly gas show responsibility on part of employer and can save lives of many who work to make company profitable. The resulting down time can however have many detrimental effects including, employee stress, safety concerns from outside agencies, and reduced production, it is therefore vitally important that we ensure that CO alarms are set off only by actual increased levels of carbon monoxide. In an effort to reach this goal there are a number of considerations to be looked at, following information is provided for that purpose.
The most common types of detectors used for Carbon Monoxide measurements are,
1) NDIR or infra-red which although is very specific to gas being measured requires a warm-up time, is fairly large, can consume larger amounts of power making it unsuitable for small or portable instruments, and is more expensive. For ranges of CO measurement in industrial uses other than Low ppm this technology is by far number one choice.
2) Solid State, while this technology is small and cost effective it is not selective enough for CO only measurements and usually has higher temperature drift making zero unstable.
3) and Electrochemical which is primary choice for majority of Carbon Monoxide analyzers on market today due to itís many benefits which include, size, weight, power, cost, and proven performance.
The remainder of this article will deal only with electrochemical sensor.
There are a number of electrochemical sensor manufacturers worldwide and each of these has a number of sensors designed for carbon monoxide measurements in different applications, choosing right one is key to success. The output from most of these sensors is very low, (pico amps per parts per million) so even subtle changes or correction procedures must be dealt with using extreme care in order to preserve integrity of signal. Sensors designed for higher concentrations of CO have a lower output per ppm which can cause it to have a