Sensor Selection for Hand-Held Portable Gas Detectors

Hand-held portable gas detectors often may be configured to have 4, 5, or even 6 different sensors installed by the factory. The sensor selection should be made by the prospective purchaser based on the intended application of the instrument after they take possession of the device. The prospective user needs to convey to the factory such possible applications as Confined Space Entry, HazMat Response, Waste Site Remediation, Indoor Air Quality, etc. The selection of on-board sensors should match up with the most likely gases and vapors associated with the customer’s application. A prospective instrument buyer should be leery of an instrument “in stock” at a local safety equipment dealer since it will probably be a common “4-Gas” unit (i.e. CO, H2S, O2, and LEL) for confined space entry applications. These devices are often severely deficient when the owner tries to apply the device to HazMat or Indoor Air Quality applications. In addition, instrument manuals, product flyers, and quickie sales presentations by local sales people often do not convey the full story of performance features as well as limitations of the instrument. Information about interference gas phenomena, cross sensitivity, lower limit of detection, correction factors, and total failure to detect are often left up to the owner to discover on his own after the purchase. Prudent prospective purchasers should first talk to sales engineers or product managers at the factory before ordering portable gas detectors. The following discussion summarizes 6 different sensor technologies that might be found on a portable gas detector with a brief description of the operating principle, sometimes with its normal useful ranges, and often closing with a caution as to certain limitation to the use of that sensor.