The Occupational Safety and Health Administration (OSHA) estimates that 1.6 million U.S. workers enter confined spaces every year. Unfortunately, nearly 100 workers are killed, and more than 5,000 other accidents occur annually in such environments. 


By definition, confined spaces have limited or restricted means for entry and exit. They are large enough that a person can enter to do work, but they are not designed for continuous occupancy. They can be above or below ground. Examples include silos, vats, hoppers, utility vaults, tanks, sewers, pipes, access shafts, truck or rail tank cars, aircraft wings, boilers, manholes and storage bins. Ditches and trenches may also be considered confined spaces if access or egress is limited. Each environment presents a unique set of potentially hazardous conditions.


Depending on the presence of hazards, the confined space may be classified as a permit-required confined space (PRCS). Under its General Industry Standards, OSHA regulations address detailed requirements for a permit that must be established for entry. Special training related to the duties each employee will perform in the confined space is critical. Electric vaults and manholes—where electrical hazards exist and only qualified workers enter—are considered enclosed spaces. They are not subject to the same regulations as a PRCS and do not require a permit. 


It is imperative to understand the difference between the requirements for a PRCS and an enclosed space.


Hazards that turn confined spaces into permit-required spaces include chemical exposures; noise; dust; explosive or flammable atmospheres; radiation; temperature extremes; poor visibility; biological hazards; uncontrolled energy; shifting or collapsing materials; and slip, trip and fall hazards. However, the most significant hazard is poor air quality and lack of oxygen. Limited oxygen could lead to a worker losing consciousness or worse.


When any of these hazards are present, steps must be taken to eliminate or control them through an entry-permit process. The permit identifies who may enter, and an attendant is assigned to monitor entry into the space. The attendant must maintain communication with the workers and perform nonentry rescues if needed. He or she may not perform any other duties. If entry is needed for rescue, the attendant must summon rescue and emergency services per employer procedures.


The permit also requires air monitoring in the space to be performed and recorded. Testing must be done before entry and periodically while work is being performed. These tests will need to gauge oxygen, flammable and combustible gas and vapor, and toxin levels for hazards, such as carbon monoxide and hydrogen sulfide.


The oxygen test must be done first. Air usually contains about 20.9 percent oxygen. By OSHA’s standards, the minimum requirement is 19.5 percent. Anything below 16 percent will diminish mental effectiveness, visual acuity and muscular coordination. 


The next test is for flammable gases and vapors. Once these tests are completed, tests must be performed for any other potential toxins that may be present. This will depend on the space being worked in.


Continuous readings for all hazards are needed while working in the space. Continuous forced-air ventilation must also be provided, and it must come from a clean source.


Procedures for enclosed spaces differ slightly from OSHA’s PRCS regulations. While enclosed spaces still include the need for testing the atmosphere before entry, the testing procedure differs in the application of forced ventilation and periodic testing. If continuous forced-air ventilation is provided, periodic testing is not required although procedures must be in place to ensure that employees will not be exposed to the hazards posed by oxygen deficiency or fire. Of course, though not required, testing is a sure way to accomplish this. However, if open flames are used in the space, tests are mandatory and are to be performed at least once each hour.


The two types of spaces also differ in attendant responsibilities and rescue. Unlike the PRCS attendant, an enclosed space attendant may perform other duties if he or she does not distract from monitoring employees within the space. The only requirement related rescue is, “Employers shall provide equipment to ensure the prompt and safe rescue of employees from the enclosed space.”


While no construction standard currently exists for a PRCS, it is critical that contractors implement procedures consistent with the general industry requirements. They can save lives. Regardless of a particular standard’s applicability, failure to protect employees can result in OSHA citation under the general duty clause of the Occupational Safety and Health Act. For more information about confined and/or enclosed spaces, visit www.osha.gov.