A reduced oxygen content in inspired air can have serious health effects. It may occur in a variety of environmental and occupational situations.
The normal oxygen content of air is 21%.
none (minimum level for safe exposure)
impaired judgment; impaired breathing
faulty judgment; rapid fatigue
difficulty breathing; death in minutes
partial pressure of oxygen in mm Hg =
= (atmospheric pressure in mm Hg) * (percent oxygen content as a whole number) / 100
According to deJong and Adams, there are 4 stages of oxygen depletion:
Signs or Symptoms
16 - 21%
none; can work or exercise without distress
12 - 16%
breathing rate and pulse are increased
10 - 14%
disturbed respirations; conscious but may be emotionally upset; abnormal fatigue with exertion
6 - 10%
nausea and vomiting; unable to move freely; unable to move or cry out; may collapse or become unconscious;
gasping respirations; convulsive movements; cardiopulmonary arrest
If toxic gases are also present, then the health effects may be even more pronounced.
A person entering an area with reduced oxygen content may require use of a positive pressure, self-contained breathing apparatus.
To read more or access our algorithms and calculators, please log in or register.