July/August 1995
Atmospheric threats are among the most dangerous and toughest to manage of confined space hazards. Easy-to-use portable gas detectors are available to help identify these threats and protect your employees.
Jeff Borsecnik
Jeff Borsecnik is an associate editor of Scrap Processing and Recycling.
The confined space standard, which has been in effect for about two years, is probably the most significant rule issued by the Occupational Safety and Health Administration (OHSA) since lockout/tagout, and it has substantial application in the recycling industry. Confined space threats to workers can be deadly, and atmospheric threats are among the most treacherous.
The standard identifies oxygen deficiency, flammable gases, and toxic gases as the main confined space atmospheric hazards. It places the burden on employers to manage the risks with care, a duty that begins with detecting potential problems. (For a primer on applying the standard to scrap processing, see Managing Confined Spaces” in July/August 1994 issue of Scrap Processing and Recycling.)
At least a handful of companies manufacture portable gas detectors specifically for confined space programs. They differ from other air-monitoring devices such as personal monitors worn by torch cutters or continuous air-monitoring equipment used by hot metal operations, which typically measure the exposure to air contaminants like lead or cadmium over time, with a laboratory evaluating the results. Confined space gas detectors, in contrast, are designed to provide an immediate warning of acute dangers.
Do You Need a Detector?
Confined space atmospheric hazards are not uncommon in scrap processing operations.
By all accounts, oxygen deficiency is the biggest threat. Oxygen can be consumed by various chemical reactions, such as rusting and combustion, and the lack of circulation in a confined space may prevent its replenishment. (Combustion also produces deadly carbon monoxide, which can build up in confined spaces.) Oxygen can also simply be displaced by other gases, especially heavier ones that might “drain” into low-lying spaces.
Excess oxygen is also a threat because it can disorient a worker, and it makes it easier for combustibles to ignite. And flammable gases, such as fuel vapors, are themselves a common confined space atmospheric threat.
Activities like welding and torch cutting can also produce atmospheric hazards when preformed in confined spaces, notes Michael Mattia, director of risk management for the Institute lf Scrap Recycling Industries (Washington, D.C.). These operations may not only consumer the oxygen in an enclosed apace, but also add an ignition source to and flammables present. Leaks in welding/torching gas lines—even pinhole bleeds over time—can also cause a buildup of dangerous gases in confined spaces.
Another common—and particularly virulent—atmospheric threat is hydrogen sulfide, which is produced by the anaerobic decomposition of organic material in a wet area, like a sere or flooded scale pit. “The problem with hydrogen sulfide is that the nerves in the nose became deadened to the smell almost immediately,” says Jeff Emond, product manager for Biosystems Inc. (Middlefield, Conn.), a manufacturer of portable gas detectors. “You think the stuff is going away, but in reality it’s continuing to kill you.
These are the most common confined space atmospheric threats in scrap processing operations, but your facility may present others.
Often these threats may be alleviated by forced-air ventilation, which also eases your confined space obligations. Even so, however, you may need a gas detector to ensure that this method is effective. Basically, says Mattia, “If you’ve got any confined spaces and you cannot prove that those spaces will not have a hazardous atmosphere, you probably will need to monitor them on a regular basis in order to enter them and be in compliance with the standard.”
Other observers also suggest that portable gas detectors may well be indispensable for recyclers’ confined space compliance. For example, even if you decide not to have your employees enter any permit-required confined spaces that ay contain safety threats—you may need a detector to document that other confined spaces at your facility thatwill need to be entered are not of the permit-required variety.
The detectors have become a “real hot topic” among the members of the National Association Supply Cooperative (NASCO-OP), the recycling industry buying co-op, according to Bob Bedard, assistant manager of the organization. But the co-op has sold fewer detectors than expected, despite many inquiries, die to prices perceived as high, surmises Bedard. Prices reported by various sources range from about $1,400 to $4,000 for complete detector kits.
Doing Your Homework
If a portable gas detector is on your shopping list, you ought to gather information and do some thinking before shopping.
The main prerequisite is knowing what sorts of atmospheric threats may appear in the confined spaces you seek to monitor. Basically, the detectors have to be configured to search for specific gases or types of gases. Familiarity with the common risks plus common-sense evaluation of your operations may suffice, or you may also need guidance from safety manuals, detector makers, or an industrial hygienist.
You should also consider the physical configuration of the confined spaces you will need to monitor. Some remote testing—from the outside space—will almost certainly be required, and the depth and configuration of the confined spaces may dictate what sort of equipment is needed. Also consider whether monitoring will be performed by workers within the space, as may be the case, for example, with especially virulent threats or hazards the workers in the space may introduce.
Other factors to figure out up front include whether the detector will be used in very wet, hot, cold, or noisy environments.
Gas Detector Basics and Choices
Once armed with details about your operation and potential use of detectors, you’re ready to examine specific detectors and the features they offer.
Sensors. Many of the gas detectors designed for confined space use have three or four separate sensors. There’s usually a sensor that measures oxygen and one that detects flammables, which represent a group of gases. Then there are typically one or two toxic gas sensors. These generally aim at particular gases, although some target gas groups, such as volatile organics. “When you low what the hazards are, your best choice is substance-specific sensors,” says Biosystems’s Emond. “But if you go into sewers [or other areas] where hazards are not well known, then you may want a broad-range sensor.” Sensors for carbon monoxide and hydrogen sulfide are the most common.
Ease of Use. When examining gas detectors, consider how easy each unit is to operate. Are digital readouts provided and are they easy to read? Can the alarms be heard in a loud area—or are visual or vibratory alarms included? (Some detectors have alarms that cannot be silenced until the unit is removed to a clean-air-area as an added safeguard.) Are all sensor readings displayed simultaneously or must you manipulate a button to switch between readings?
Keep in mind that your employees are likely to be using the detector in awkward circumstances, perhaps with poor light and while wearing gloves, goggles, or other protective gear.
Flexibility. Consider what control the user has over the setup of the machine. Are alarms pre-set or user-set? Of factory-set, are the settings appropriate for your needs?
Some detectors have several different modes of operation, to serve users ranging from the welder to the environmental technician (perhaps with concerns broader than confined spaces). Consider whether such options are necessary to meet your needs—and of they complicate use of the detector.
Batteries. There are several choices to be considered when it comes to powering gas detectors: Disposable alkalines are easy to use and may be the best choice for the infrequent user, says Cary Bush, technical service representative for Lab Safety Supply (Janesville, Wis.), a catalog company that sells six brands of confined space gas detectors. Rechargeable nickel-cadmium or lead-acid batteries, on the other hand, require more care than disposables bit are less expensive in the long run. And within the rechargeable category, nickel-cadmiums may be more finicky than lead-acids, but they are also lighter. In any case, if you opt for rechargeables, check out how long recharging takes—it might be as much as 16 hours.
Another thing to consider: Does the detector have a low-battery-power indicator that can be heard in all likely settings?
Design/Construction. Several factors about the design and construction of a detector should be examined, in addition to its ease of operation. First, is it certifiedintrinsically safe, a term that means “it is physically designed so that if you pull a flammable gas in there, the equipment won’t blow up un your hands,” explains Peggy Rumiez, a certified industrial hygienist with CAN Insurance (Chicago). Second, the unit should be shielded from radio frequency and electromagnetic interference.
Durable construction is also important, but it may be tough to evaluate based on looks—not to mention product literature—alone. Still, the manufacturer’s warranty may provide a clue.
Accessories and Extras. Remote testing requires some kind of pump and hose to draw in samples. The pump may be internal or external to the unit, manually operated or motorized. Internal pumps might be more convenient, yet make the instrument heavier and larger, and, hence, less appealing for use within a confined space. In any case, evaluate whether these accessories appear easy to assemble and use.
Some gas detectors are very sophisticated, capable of collecting detailed information and perhaps downloading it to a computer. Consider whether you will use these sophisticated features and if the recordkeeping ease is worth the added cost.
Technical Support. Several sources suggest examining the support the manufacturer provides. The first-time buyer probably needs some help in picking the right detector and sensors. But probably even more important is ongoing user support. Consider: Is the documentation provided with the detector clear and easy to use? Are knowledgeable telephone support and replacement parts available when needed?
Calibration and Maintenance
Although built for rugged use, gas detectors require careful upkeep.
Key to the detectors’ performance is calibration. “It doesn’t matter how expensive or sophisticated the gear is, the weakest link is how well you maintain calibration,” says Biosystems’s Emond. “If the accuracy is not verified and maintained, then the equipment is useless at best, and dangerous at worst, because it provides a false sense of security.
Although the detectors may be factory-calibrated and ready to go upon delivery, users must ensure they remain accurate. Calibration is necessary not only to make sure readings are on target, but also to verify that the sensors, which have limited life span (averaging about 18 to 24 months), are not burned out, says Emond. The risk is that some, like oxygen sensors, fail in a “safe” manner—they read “0” when dead—others aimed at dangerous gases fail in an “unsafe” manner, in which they are simply unresponsive in the presence of material they are supposed to detect.
The exact methods of calibration vary from manufacturer to manufacturer. One may require a periodic return to the factory (which raises issues of convenience and cost). Others, apparently including most new machines, can be checked and recalibrated by the used. This process involves exposing the sensors to sample gases of the type the sensors are designed to read and at a known concentration so the readings can be checked—there is no sure-fire way to test the sensors electronically, notes Emond.
The confined space standard requires that calibration be performed in the manner and frequency dictated by the manufacturer, which may range widely. They should also be recalibrated if they’ve been dropped or submerged in water, suggests NASCO-OP’s Bedard.
Beyond calibration, the gas detectors should simply be treated with care, perhaps like you would handle an expensive camera. For example, they should be kept clean, away from solvent fumes, and never brought abruptly from a cold area to a warm, moist one, which may cause internal condensation.
Wise Use
There’s a caveat to this story.
The most carefully selected and accurate gas detector can’t protect workers if it’s not properly used. Users must be familiar with the confined spaces being monitored and the associated hazards. They must know how to sample accurately—a detailed, painstaking process—and how to respond to the results. “Most of the detectors are made so you can just turn them on and use them,” says Bush. “The problem is what happens after that. If the guy ignores the alarm…”
Atmospheric threats are among the most dangerous and toughest to manage of confined space hazards. Easy-to-use portable gas detectors are available to help identify these threats and protect your employees.