Appropriate Levels

• OSHA requires that workers breathe at least 19.5 percent oxygen. If the available oxygen falls below this level, the employer is required to provide a self-contained breathing apparatus.
  
  

Rationale

• OSHA states that the rationale behind this regulation is that air is considered to be oxygen-deficient once it falls below 19.5 percent. Once it falls below this point, workers can begin to exhibit symptoms quickly.
  
  

Oxygen-Deprivation Symptoms

• According to OSHA, symptoms of oxygen deprivation can include heavy breathing, accelerated heartbeat and impaired thinking. Lower oxygen levels can result in even more dangerous symptoms like nausea, vomiting and unconsciousness. These symptoms are especially dangerous if the employee is engaging in an activity such as climbing a ladder.