Wait! Did You Check Your Gas Detector?

Confined-space entry deaths continue to make headlines. Learn how the proper gas detector could save your life.

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Just a few months ago, two men were killed and one man was hospitalized when they were overcome by toxic fumes while working in an underground sewer in Phoenix. According to a local online news report, the men were working inside the 15-foot-deep sewer without protective gear, and one emerged behaving lethargically. An investigation detected high levels of hydrogen cyanide in the sewer.

Sadly, these stories make the news more often than they should. In addition to protective gear, anyone working in a confined space should use a gas detector to detect harmful toxic gas.

Perhaps it’s easy to assume you’ll be fine without a gas detector or confined-space gear because you’ve climbed into a pipe without those things and come out unscathed hundreds of times before. Familiarity breeds complacency. Someday, when you least expect it, a simple hand-held device could help save your life.

That brings us to sorting through all the available options to choose the one that best suits your needs.

Should you choose a portable gas detector capable of detecting the one hazardous gas you’re most likely to encounter, or a multigas meter, capable of detecting several gases simultaneously?

“Sewer contractors usually know which gases they’re likely to encounter,” says Rick Wanek, industry market manager, portable instruments with Pittsburgh-based Dräger Safety Inc. “If they run into anything unusual, like chlorine used to treat wastewater, they’re usually informed before they get to the site.”

Bells and whistles
Meters make use of a number of technologies appropriate to each gas they’re designed to detect. A multimeter might use multiple methods to detect a range of gases. Infrared sensors detect gas concentrations by shining infrared light through the sample.

Electrochemical sensors read electrical currents generated by the interaction of specific chemicals and a target gas. Catalytic sensors ignite small samples of gases, such as methane, and measure the resistance between two filaments.

“In a sewer setting you would want to detect four standard gases — methane, oxygen, hydrogen sulfide and carbon monoxide,” Wanek says.

Why oxygen? Because a meter capable of detecting methane does so thorough electronic combustion of microscopic methane samples, which requires oxygen.

Anything but ordinary
Occasionally, you might be required to work in confined spaces containing an additional gas.

“It may be more economical ... to buy additional single-gas meters to deal with specific problems related to the situation in which they’re working," Wanek says. "Generally workers are reluctant to carry two meters, but that may be the least expensive way to go.”

Alternate testing devices can also be used. Dräger tubes, for example, are glass ampoules containing a number of reagents that can detect specific gases in various environments.

“You pump the surrounding atmosphere through the tubes to determine peak concentrations,” says Wanek. “However, they’re best used in limited areas. Carrying a portable gas meter is like carrying a video camera running continuously, while using the tubes is more like taking a snapshot of a limited environment, such as a sewer, shaft, tank or other confined space.”

Chip off the old block
Another solution is a chip system, a higher-tech version of the tubes in which a portable unit can be outfitted with a choice of more than 55 gas-specific chips. However, like the tubes, the chip system provides only a snapshot of gas concentrations.

Portable meter technology continues to advance.

“The most dramatic change is in the microprocessors used to analyze the readings,” Wanek says. “For example, if you’re exposed to 50 ppm of a certain gas each day, and 60 ppm for a very short time, the microprocessor is able to calculate what is considered an acceptable exposure for the day through time-weighted averages.”

A good portable gas detector, however, is no substitute for safe work practices, notes Wanek. “The detector will alert you to the hazard,” he says. “But regulations dictate that you need a spotter to help get you out of there if there’s trouble.”

Keep your workers safe and avoid dangerous — and deadly — activities with these safety products:

The Multi Gas Clip Pump (MGC Pump) portable multi-gas detector from Gas Clip Technologies is ideal for attendant applications in confined-space entry.

The smallest gas detection instrument for up to five gases, the Dräger X-am 5000 belongs to a new generation of detectors developed especially for personal monitoring.

DuraBlast double-coated PVC-on-polyester safety suits from Milwaukee Rubber Products are engineered specially for hydroblasting and hydroexcavation applications.

HM Impact gloves from Cestusline have DNX Grip technology and a one-piece palm pattern with cut level 2 that is oil and water resistant.

ProOperator protective gloves from TST Sweden AB are tested and certified for pressurized liquids, such as water and hydraulic fluid.


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