OHS Canada Magazine

Gas Encounters of the Work Kind

May 18, 2016
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By Jeff Cottrill

Dangerous substances or impurities in the air are a common risk in many industries and professions, from oil and gas, power generation, mining and firefighting to emergency response and jobs involving dangerous materials. This hazard is not exclusive to work in confined spaces; some workers face the risk of invisible, toxic gases even in the open air. That is why gas-detection devices are essential to so many professions.

But with all the varieties of instruments on the market, how should an employer determine what kind of device is right for his or her workers? John Raimondi — the marketing manager for oil, gas and petrochemical products with MSA Safety Incorporated in Cranberry Township, Pennsylvania — notes a few important factors to consider.

“The durability of the detector’s very important,” says Raimondi, whose company manufactures and sells detectors for combustible gas, toxic substances and oxygen. “A lot of our customers are in some pretty dirty and pretty rough environments.” He also recommends ease of use as another major consideration: “If you could make something fairly complex into something that is simply understood and managed, I think that that is definitely something that you’d want to use.” Of course, the product should also be in line with whatever regulatory requirements apply to the company’s country, state or province, he adds.

But the most important factor Raimondi points out is, obviously, that the device will detect the specific substances that are likely to be present in the workplace, based on a formal hazard assessment by a qualified professional. Bob Henderson, the president of Good for Gas Instrumentation (GfG) in Ann Arbor, Michigan, fully agrees.

“The first thing that you need to do is to have an understanding of what types of atmospheric hazards might be present, and that includes present in all areas where your workers may be exposed to dangerous conditions,” says Henderson. “That defines what you do next.”

Henderson cites Canada’s oil and gas sector as an example of an industry with specific hazards. “In a lot of Canadian worksites involved in oil production, the number one issue that is concerning would be hydrogen-sulphide exposure. If that is the case, then all you really need to do to keep your workers safe is to use a single-sensor H2S monitor,” he explains. But occupational health and safety authorities in the western provinces may prefer oil and gas companies to use standard four-sensor instruments that detect oxygen, carbon monoxide and lower-explosive-limit gases as well, since hydrogen sulphide is “part of a matrix of gases,” Henderson adds.

Calibration to prevent inhalation

Another factor worth thinking about, according to Raimondi, is lower cost of maintenance. “Over the life of the product, one of the biggest costs to a customer is the cost of calibration,” he notes. “Whatever can be done in terms of reduction of calibration-gas usage and lowering the cost and time of calibration is something that we would recommend most customers take a look at in their evaluation.”

Calibration and bump tests are the two main ways that users of these devices need to keep them working at full power and lasting longer. But what’s the difference between them? “What a calibration does is, it brings the sensors back to normal against a fixed and known quantity of gas. Over time, those can drift,” Raimondi continues. “Temperature trends, humidity, things like that, can affect the sensor sensitivity.” A bump test, or bump check, is a test that determines whether the sensors in the instrument are going to work during immediate use, by exposing them to limited concentrations of the gases they are designed to detect.

“The calibration is more of a longer-term thing that you wouldn’t need to do all the time, but a bump test is something that we always recommend be performed before each day’s use,” explains Raimondi. Companies who sell gas detectors usually advise employers to calibrate the devices twice or four times a year; sometimes, they even recommend monthly calibration. “But a bump test is something that we always recommend be performed before each day’s use.” This way, the user can find out right away if the sensors are working properly or if the path to the sensor is blocked, he adds.

Calibration is not the only factor that can affect the cost of a gas-detection device. The upfront price of buying an instrument can vary, depending on the number of sensors it uses and additional features it has. “The length of warranty and also some of the pumps versus the diffusion-based instruments, where if you have something with a pump, those can cost a little bit more,” says Raimondi. “But the total cost of ownership, really the biggest driver on that, is how much calibration gas is going to be used in order to perform maintenance like calibration and bump testing.”

Sensor trends

In addition to reduction of costs, Henderson notes a current trend in which manufacturers of sensors are trying to reduce the power required for them to function.

“That’s one of the drivers with some of the infrared sensors that are available in some models of instruments,” he explains. “They use very little power, which means you can go weeks or even months on a single charge rather than the way it’s been in the past, with higher-powered sensors that would only run for 12 hours on a charge or a set of batteries. There are tradeoffs, of course, but that’s one emergent trend.”

Varying the sizes of sensors in gas-detection devices is another trend among manufacturers, Henderson continues. “Some manufacturers take the approach that using larger-format sensors is safer, better, more accurate. Other manufacturers take the approach that reducing the size of the sensors allows you to reduce the size and the cost of the instrument.”

New technologies are always cropping up in the market as well. Wireless devices are available for situations in which workers enter confined spaces: this allows one worker to stand outside the space with a device that picks up information from the other workers’ instruments. There are even detectors with GPS capability out there.

Whatever the technological advance, the basic design remains the same. It is up to the employer to determine what functions are necessary — and what ones are not — for workers who need to protect themselves from invisible threats.

Jeff Cottrill is the editor of Canadian Occupational Health and Safety News.

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