An abbreviation for Dangerous Substances and Explosive Atmospheres Regulations 2002 of the UK’s Health and Safety Executive (HSE). The regulations are intended to protect people from dangerous substances by putting particular duties on employers and self-employed people to protect workers in the workplace as well as members of the public. The regulations require that employers identify the substances that present a risk and put control measures in place to remove the risks or to control them.

http://www.hse.gov.uk/fireandexplosion/dsear.htm Official website of the Health and Safety Executive, DSEAR regulations.