Hazardous energy in occupational safety and health is any source of energy (including electrical, mechanical, thermal, chemical, hydraulic, and pneumatic sources of energy) that "can be hazardous to workers", such as from discharge of stored energy. Failure to control the unexpected release of energy can lead to machine-related injuries or fatalities. The risk from these sources of energy can be controlled in a number of ways, including access control procedures such as lockout-tagout.