Oxygen Deficient Environment

The air that we breathe contains 21 percent oxygen. An oxygen deficient atmosphere contains less than 19.5 percent oxygen. Oxygen deficiency, or lack of oxygen, can cause fatigue, loss of consciousness, and even death. Oxygen deficient atmospheres in a confined space may be due to nitrogen intrusion, welding, grinding, oxidation, coating, or as we saw in an earlier case study, carbon dioxide buildup after a vacuum test.

The number one cause of asphyxiation is oxygen deprivation. Here are some typical symptoms of exposure to different oxygen levels:

• 19.5% - Minimum level for normal breathing
• 15-19% - Decreased ability to work strenuously, impaired judgment and coordination, increased pulse
• 12-14% - Breathing difficulty, impaired judgment and coordination
• 10-12% - Respiration increases, blue coloring around lips and mouth
• 8-10% - Mental fatigue, fainting, nausea, unconsciousness, ashen face, vomiting
• 6-8% - Recovery depends on duration of exposure, as follows:
  • 4-5 minutes: recovery is possible with treatment
  • 6 minutes: 50% fatal
  • 8 minutes: 100% fatal
• 4-6% - Coma within 40 seconds and death

As an entrant or attendant (that is, the person entering the space or the person keeping watch), it is vital that you are able to recognize these symptoms. If you notice them in yourself or in a coworker, perform emergency procedures immediately.

To learn more about Confined Spaces visit our Construction Confined Spaces Online Training web page.