Follow these simple, common sense rules and it’s extremely unlikely that your entry into a confined space will result in injury or death. But break them, and it’s only a matter of time before you get someone killed or injured. These general rules are the distilled wisdom of confined space operations, consolidated from many sources, and with the exception of the first rule, they are not in any particular order.

The only reliable method for accurate detection of atmospheric problems is instrument monitoring. Basic confined space atmospheric monitoring should routinely include oxygen concentration and flammable gases and vapors. OSHA regulations require the oxygen concentration to be between 19.5 and 23.5 percent and flammable vapors or gases to be below ten percent of the lower explosive limit (LEL).