What is the PEL for oxygen, including its limits?

The permissible exposure limits (PEL) for oxygen in the context of workplace safety are crucial for ensuring employee health and safety. The correct answer specifies that the acceptable levels of oxygen in the air should range from 19.5% to 23.5%. This range is essential because concentrations of oxygen below 19.5% can lead to symptoms of hypoxia, which can impair cognitive function and physical capability. Conversely, levels above 23.5% can increase the risk of fire and explosion due to the enhanced flammability of materials.

Understanding these limits helps workers recognize safe working conditions, especially in environments where there may be changes in atmospheric composition due to chemical processes or confined spaces. The other options do not reflect the established standards for oxygen levels, making the specified range critical for maintaining safe working conditions in various construction and industrial environments.