Millions of people work in confined spaces every year. More attention should be given to the danger of toxic, flammable, or asphyxiating gas accumulating in confined workplaces.
Two common types of hazardous confined spaces found in the industrial workplace are:
- Open-top spaces with a depth that restricts the natural movement of air at the bottom
- Limited-access spaces with narrow entry and exit openings
Examples of open-top spaces that collect gases at the bottom are degreasers, pits, vats, and certain kinds of storage tanks. The natural movement of air is restricted at the bottom by depth. Gases that are heavier than air — butane, propane, and other hydrocarbons — sink to the bottom of the confined area where they collect to dangerous levels.
Sewers, septic tanks, silos, manholes, pipelines, and utility vaults are common examples of limited-access spaces. Like open-top spaces, these confined areas may retain gases that are heavier than air for hours or days.
The National Institute for Occupational Safety and Health found that in more than a third of confined space accidents, the dangerous atmosphere did not exist when the worker entered the confined space. Sometimes the products brought in and used in the work space create a toxic gas. While our product safety laws require manufacturers to warn of the danger created by using their products in foreseeable environments, this is not always done.
Most injuries in confined spaces occur when those responsible for workplace safety fail to:
- Test the air for dangerous gases before allowing workers to enter
- Alert workers to the hazards posed by working in confined spaces
- Disconnect heavy mechanical equipment inside the space while work is performed
- Disconnect or block all liquid, chemical, and steam lines into the space
- Continuously monitor the space for atmospheric changes.
Tragically, over half of the workers who die in confined spaces do so while attempting to rescue other workers overcome by toxic gases. NIOSH therefore recommends that a standby person remain outside the space and keep in constant communication with the workers inside. When an emergency arises, the standby person should not enter the space until help arrives, and then only with the proper protective equipment and life lines.