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Regardless of the industry, a confined space can be a dangerous, even deadly, work environment. A key part of a confined space entry program is effective use of calibrated, direct-reading as monitors to evaluate a potentially hazardous atmosphere. Those responsible for air monitoring must know the nature of potential hazards and be confident in the use and maintenance of air monitoring instrumentation.
In 1993, OSHA implemented a new standard, 29 CFR 1910.146, to protect workers in confined spaces. Employers now must identify all permit-required confined spaces in their workplaces, prevent unauthorized entry, and, by means of a permit program, protect authorized workers from hazards. The rule, which includes permit-required entry procedures and other safety measures, is intended to protect workers from toxic, explosive, or asphyxiating atmospheres and from engulfment. The regulation, currently in effect, has been estimated to prevent more than 50 fatalities and more than 5,000 serious injuries each year.
Before an employee enters a permit-required confined space, the internal atmosphere must be tested with a calibrated, direct-reading instrument for the following conditions in the order given: oxygen content, flammable gases and vapors, and potential toxic air contaminants. Non-permit confined spaces, according to OSHA, are confined spaces that do not actually or potentially contain atmospheric hazards capable of causing death or serious physical harm.
Industry-Specific Hazards
The nature of confined space hazards may vary greatly from one industry to the next. In any industry, the most critical gas test in confined space work is for oxygen content, which can be depleted as a result of restricted air flow in the space. If oxygen content in breathing air is lower than normal levels, it can be debilitating and lethal because its physiological effects are not felt until it is too late.
Low oxygen content can be caused by the presence of a number of gases, including methane, carbon monoxide, and carbon dioxide. It can also be caused by the rusting of metal, combustion due to welding and hot work, bacterial activity, or air consumption by workers. Additionally, oxygen must be monitored when workers use bulk nitrogen for vessel inserting or use other blanketing gases such as argon.
An oxygen level exceeding 23 percent by volume creates a fire hazard. If ignition occurs, such flammable materials...