There are three major categories of hazardous gases.
Combustible gases pose a risk to personnel and facilities through fire or explosion.
Toxic gases create both immediate and long term risk to personnel. Oxygen displacing gases deplete workers' oxygen supply in confined spaces. Risk can be reduced through a properly designed gas risk management program. A successful program needs to first, identify the hazards at the facility, then assess the risk of a hazardous event to the plant, personnel, the community and the environment. Next, the program needs to comply with insurance, legal and regulatory requirements.