Entering a permit space can be fatal for an employee when the oxygen level is:

The correct choice emphasizes critical safety thresholds for oxygen levels in permit spaces. A concentration of oxygen below 19.5 percent is considered an oxygen-deficient atmosphere, which poses a serious risk of suffocation and can be fatal. Conversely, oxygen concentrations above 23.5 percent create a potential for fire and explosion hazards, as high oxygen levels can significantly increase the flammability of materials.

These levels are established by safety regulations such as those from OSHA and NIOSH to ensure worker safety in environments where the air quality may be compromised. Maintaining oxygen levels within the safe range of 19.5 to 23.5 percent is essential in preventing life-threatening situations when working in confined spaces.

The other options do not reflect the accepted safety limits for oxygen concentration. They either set the thresholds too high or too low, which could lead to misunderstanding and mismanagement of safety protocols in permit-required confined spaces.