US Army
U.S. Army Reserve Pvt. Kenneth Collins, 376th Engineer Firefighter Detachment, pulls himself from a confined space familiarization tube at Combat Support Training Exercise (CSTX) 86-18-02 at Fort McCoy, Wis., August 13, 2018.
A space is confined if it has a limited or restricted entry or exit point.
"Confined spaces include, but are not limited to, tanks, vessels, silos, storage bins, hoppers, vaults, pits, manholes, tunnels, equipment housings, ductwork, pipelines, etc.," according to the Occupational Safety and Health Administration.
And the US military trains for all different kinds of scenarios in such spaces.
Here's what they do.