Virginia Tech®home

Signs and Symptoms of Oxygen Deficiency

Confined Spaces Quick Links


Oxygen Deficiency Signs and Symptoms

The brain is the body organ most sensitive to lack of oxygen. Low oxygen concentrations can include giddiness, mental confusion, loss of judgment, loss of coordination, weakness, nausea, fainting, loss of consciousness, and death.

  • 20.9 percent: Normal atmospheric oxygen content.
  • 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, death.

Emergency Response and First Aid Measures

  • Rescue personnel or non-entry rescue: Move victim to fresh air immediately.
  • If victim is not breathing, begin CPR.
  • If victim is breathing, place in recovery position to assist with breathing and prevent inhalation of stomach contents if vomiting occurs.

Contact Information

Robin McCall-Miller, Occupational Safety Program Manager

Phone: 540-231-2341
Email: rmmiller@vt.edu