Chemistry and Chemical Disasters. A vapor or gas which can cause unconsciousness or death by suffocation (lack of oxygen). Asphyxiation is one of the principal potential hazards of working in confined spaces
US Department of Labor, Glossary of Terms - Occupational Safety & Health Administration, OSHA Office of Training and Education, Construction Safety and Health Outreach Program, Washington, D.C., USA 1996. https://www.osha.gov/doc/outreachtraining/htmlfile s/hazglos.html, (OSHA/ Const - Amer) {614}