Overview: Portable gas detectors are essential safety equipment for contractors who face potential exposure to hazardous gases. Choosing the right equipment can help save money while ensuring workers are alerted to critical workplace dangers
Contractors who work in a wide range of environments understand the need to protect themselves with sensitive portable monitors capable of detecting hazardous gases.
A wealth of options, however, can make selection a complicated matter. Should contractors buy meters capable of detecting the one gas they’re most likely to encounter, or buy multi-gas meters, capable of detecting up to five gases simultaneously? When outfitting an entire crew with similar protection, cost becomes an even more important factor.
“In many cases, contractors called onto a site are usually informed of the type of gas hazards they may encounter,” says Rick Wanek, industry market manager, portable instruments with Pittsburgh-based Dräger Safety Inc. (Draeger). “Often the way portable detectors are selected is to either ask the people on the site what they’re using and buy that, or to go out and buy the cheapest detector for the job.”
Contractors who actually need to enter a mine have a relatively easy selection task. Any gas detector used in a mine must be certified by the Mine Safety and Health Administration in the U.S. or by the respective provincial authority in Canada. Further, many other settings require the meters to be approved by Underwriters Laboratories Inc. or the Canadian Standards Association.
Although Wanek says occasional counterfeit equipment reaches the market, the perpetrators are quickly eliminated. “In order to sell, they have to advertise, and organizations like Underwriters Laboratories are quick to defend their trademark,” he notes.
RIGOROUS APPROVALS
The testing is both rigorous and expensive. That’s one reason there are only a handful of suppliers in the market – the cost of testing eliminates casual competitors. For MSHA approval, for example, the meter considered for approval must function to spec the first time it’s tested. If not, the prototype unit is returned and must be altered in some fashion – either through software adjustments or recalibration – and the next approval process begins from scratch.
The meters make use of a number of technologies appropriate to each gas they’re designed to detect. A multi-meter may use multiple methods to detect a range of gases. Infrared sensors detect gas concentrations by shining infrared spectrum light through the sample. Electrochemical sensors read the electrical currents generated by the interaction of specific chemicals and a target gas. More complex catalytic sensors ignite small samples of gases such as methane and measure the resistance between two filaments.
Dräger portable detectors run from about $200 for single-gas units to around $1,500 for sophisticated multi-gas units.
“The mining industry leans toward multi-gas meters,” says Wanek. “In a coal mine you would at least want to have methane detection, but you could easily add oxygen and carbon monoxide sensors, and where diesel engines are used, nitrogen dioxide. Some mines also have issues with hydrogen sulfide.”
Why oxygen? Because a meter capable of detecting methane does so through electronic combustion of microscopic methane samples – which requires the presence of oxygen to complete the combustion process.
A meter capable of detecting those five gases would also cover contractors who work in the oil patch or in natural-gas fields.
“After that point, it may actually be more economical for contractors to buy additional single-gas meters to deal with specific problems related to the field in which they’re working,” says Wanek. “Generally workers are reluctant to carry two meters, but that may be the least expensive way to go on a case-by-case basis.”
