OSHA Oxygen Concentration Standards
Confined spaces such as utility vaults, manholes, storage tanks and sewer silos pose a hazard to workers, particularly when there is oxygen depletion. The Occupational Safety and Health Administration (OSHA) has rules for working in confined spaces, including acceptable oxygen concentration standards and situations in which employers must provide employees with respiratory protection.
Oxygen-Deficient Hazardous AtmosphereOSHA regulations define a confined space as any area with the following characteristics: the area is large enough for an employee to perform work; access to the area is limited; and the area is not intended to be a continually occupied work space. Employees typically enter a confined space to test equipment, perform maintenance or because of an emergency. When the oxygen concentration in any confined space dips below 19.5 percent, OSHA considers this an oxygen-deficient hazardous atmosphere that can threaten life or health. OSHA mandates that employers must implement procedures to warn employees of the oxygen-deficient hazard before they enter the confined space and provide necessary personal protection equipment.
Permit RequirementA confined space with a potentially oxygen-deficient hazardous atmosphere is known as a "permit-required confined space" in OSHA regulations. The employer is required to have a written permit to control entry into such a space. The permit must include all information necessary to ensure employee safety and comply with OSHA standard 1910.146(f), which requires, among other things, that the permit specify the name of all employees entering the confined space, the name of the supervisor authorizing entry, communication procedures, and the equipment required for entry.
Personal Protection EquipmentEmployers must provide employees with air-supplying respirators such as a self-contained breathing apparatus or a supplied-air respirator with auxiliary self-contained air supply. OSHA regulations also require the employer to implement a written respiratory protection program to trains employees in using respirators.
Additional ConsiderationsOxygen concentration level is not the only factor that determines whether a permit-required confined space is safe for employees to enter. The normal oxygen concentration for ambient air is 20.9 percent. Any time the concentration level is less, even at 19.5 percent or slightly above, the employer must determine the cause. Toxic fumes from a solvent can make the space unsuitable for employees, for instance.
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