The American Industrial Hygiene Association (AIHA) recommends 20 complete air changes per hour, or one every 3 minutes, for confined spaces. Ventilation requirements vary depending on the material being ventilated. Ensure that the air supply is fresh and uncontaminated by flammables, toxins, or other harmful substances.
The atmosphere within the space must be periodically tested to ensure that continuous forced air ventilation prevents hazardous conditions. Employees entering the space, or their authorized representatives, should be given the opportunity to observe this testing.
If a hazardous atmosphere is detected during entry:
Each employee must exit the space immediately.
The space must be assessed to determine how the hazardous atmosphere developed, and measures must be implemented to protect employees from the hazard before any future entry occurs.