The reason for the occurrence of the "hazardous atmosphere" in Confined Space are:
1. The oxygen content below 19.5% or above 23.5%
2. The build-up of toxic gas is greater than Permissible Exposure Limit (PEL)
3. The build-up of flammable gas is over 10% of its Lower Explosive Limit
4. Any other atmospheric condition that is Immediately Dangerous To Life or Health
