An enclosed space that has the following characteristics: its primary function is something other than human occupancy; it has restricted entry and exit; and it may contain potential or known hazards. Examples of confined spaces include, but are not limited to, tanks, silos, vessels, pits, sewers, pipelines, tank cars, boilers, septic tanks, and utility vaults. Tanks and other structures under construction may not be considered confined spaces until completely closed. Restricted entry and exit means physical impediment of the body, e.g., use of the hands or contortion of the body to enter into or exit from the confined space.