Wastewater Treatment Operator Certification Practice Test

When is a confined space considered oxygen deficient?

1. In atmosphere where oxygen content is less than 19.5% by volume

2. In atmosphere where oxygen content is less than 23.5% by volume

3. In atmosphere where oxygen content is more than 23.5% by volume

4. In atmosphere where oxygen content is less than 29.5% by volume

The correct answer is: In atmosphere where oxygen content is less than 19.5% by volume

A confined space is considered oxygen deficient when the atmosphere contains less than 19.5% oxygen by volume. This standard is crucial in ensuring the safety of individuals who may enter such spaces, as oxygen levels below this threshold can lead to impaired cognitive function, unconsciousness, and even death. The Occupational Safety and Health Administration (OSHA) and the National Fire Protection Association (NFPA) define safe levels of atmospheric oxygen as being between 19.5% and 23.5%. Levels below 19.5% indicate a deficiency and present serious risks, while levels above 23.5% suggest a potential for hyperoxia, which can also be dangerous. Thus, the correct identification of an oxygen-deficient environment helps in implementing necessary safety measures and protocols to protect workers and emergency responders.