Safety professionals and others have recognized the hazard of entering a confined space or dangerous area where toxic gases are present. However, the more dangerous hazard is often oxygen deficiency. Normal air contains 20.9 percent oxygen and the rest is nitrogen and other gases. OSHA defines oxygen deficient as any atmosphere that contains less than 19.5 percent oxygen or oxygen enriched as any atmosphere that contains more than 22 percent.
Effects of an oxygen deficient atmosphere include:
- 19.5 percent: Minimum level for confined space entry, if alarm sounds on monitor exit the space immediately.
- 19 percent: Adverse physiological effects occur, but they may not be noticeable, such as impaired judgment/thinking/attention.
- 15 percent: Reduced intellectual and physical performance without awareness: muscle coordination begins to decrease, the heart rate increases, rapid fatigue is experienced and/or inability to work strenuously, and respirations increase.
- 12 percent: Judgment is impaired, faulty coordination, emotional upset, abnormal fatigue upon exertion.
- 10 percent: Very poor judgment and coordination, impaired respirations that may result in permanent heart damage, fainting within a few minutes without warning, nausea, and vomiting.
- Less than 10 percent: Inability to move, fainting almost immediately, loss of consciousness, convulsions, and death.
In order to determine if the air in a confined space or area is safe to breathe, it is critical to test the oxygen levels before entering the location. Once inside, continuous or periodic monitoring of oxygen levels is needed. Fixed and/or handheld monitoring devices should be readily available, their use required before entering, and able to alert users to any breathing hazard. Portable gas monitors are available with an oxygen sensor, a flammable sensor, and a range of toxic gas sensors.
Training is most important for those working in an oxygen deficient atmosphere. They should:
- Know the signs of oxygen deprivation.
- Identify permitted confined spaces and areas where oxygen deficiency may be present.
- Identify the duties of the entrant, attendant, and supervisor.
- Demonstrate the use of gas monitoring devices.
- Demonstrate how to enter a confined space and the use of harnesses, respirators, and other equipment.
- Understand how to eliminate oxygen through ventilation systems.
- Understand rescue procedures.
Confined spaces can be found in any industry. It is important that they be identified and determined whether oxygen deficient and other hazardous atmospheres can be present. All necessary steps should be taken before anyone enters a confined space or other hazardous location.
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