Examples of confined spaces include manholes, sewer digestors and silos, tunnels, pumping stations, and utility vaults. There are many hazards in confined spaces. Workers can become unconscious and die from a lack of oxygen. At other times, there may be too much oxygen, or other chemicals can be present that can catch fire or explode. Poisonous gases and vapors, such as hydrogen sulfide or carbon monoxide, may also build up in a confined space.
Confined spaces can also pose physical hazards.
They can be very hot or cold. Such an area can be very loud. Workers can slip on wet surfaces. Grain, sand or gravel can bury a worker. Trenching and Excavations Working in an area that has been dug up can be very dangerous.