Lockout/tagout is an important safety procedure to prevent accidental movement or operation of machinery and electrical equipment when it might endanger workers. For example, a piece of machinery that needs cleaning or repair is completely shut down. Padlocks or other safeguards are installed to stop unauthorized persons from turning on the machinery. A "Do Not Start" sign is mounted on the mixer's control switches. Similar safety procedures also apply to equipment that might roll, fall, or move onto a worker after being shut down. In a study of accidental deaths caused by failure to observe lockout/tagout procedures, OSHA found that accidents happened most often due to the following four causes:
- Failure to deactivate machinery: Workers should always turn off machinery when it's not in use.
- Accidental activation: This type of accident usually happens when a worker starts up a machine without realizing that other workers might get hurt.
- Equipment failure or malfunction: Sometimes accidents happen when workers try to use machinery they know is not working properly.
- Procedures that are inadequate or not followed: Many accidental deaths occur because lockout/tagout procedures do not exist or are not enforced.