What is the minimum percentage of oxygen considered safe for entry according to EPA?

The minimum percentage of oxygen considered safe for entry, according to the Environmental Protection Agency (EPA), is 19.5%. This level is critical because oxygen is necessary for human respiration. If the oxygen concentration falls below this threshold, there can be an increased risk of suffocation and other health hazards.

It is established that oxygen levels in the atmosphere should ideally be around 21%, which is the concentration found in the air we normally breathe. However, any level below 19.5% can pose a significant risk, indicating that the environment may not be safe for personnel to enter without proper precautions. Thus, the 19.5% level serves as a safety baseline in environments where oxygen could be displaced, such as underground storage tank sites or other confined spaces.