What percentage of oxygen (O2) is required in the tank for safe entry?

For safe entry into a tank, a minimum oxygen level of 21% is required to ensure a safe environment for personnel. This concentration is vital because it aligns with the standard atmospheric conditions where humans can function normally without risk of asphyxiation or exposure to low oxygen levels.

Oxygen levels below this threshold can lead to safety hazards; specifically, concentrations lower than 19.5% are considered unsafe for breathing according to the Occupational Safety and Health Administration (OSHA) guidelines. Ensuring that the oxygen level is at 21% or above helps mitigate the risks of asphyxiation and supports a safe working environment.

While other options may suggest higher percentages, they do not reflect the necessary minimum requirement for safe entry into confined spaces such as tanks. Proper monitoring and maintaining the right levels of oxygen are essential for the safety of personnel involved in tank operations.