PEPCON disaster happened in 1988.
Luzhniki disaster happened in 1982.
Ibrox disaster happened in 1971.
Knockshinnoch Disaster happened in 1950.
Seveso disaster happened in 1976.
Abbeystead disaster happened in 1984.
The chemical fire and explosions at the Pacific Engineering Production Company of Nevada occurred in http://www.answers.com/topic/henderson-nevada?initiator=WANS on May 4, 1988.
A disaster can happen at any time. The trigger depends on the kind of disaster.
Patria disaster happened in 1940.
Westfield disaster happened in 1871.
Ryongchon disaster happened in 2004.
Flixborough disaster happened in 1974.
Kaprun disaster happened in 2000.
Feyzin disaster happened in 1966.
Kyshtym disaster happened in 1957.
Spyros disaster happened in 1978.
Abbeystead disaster happened in 1984.
Niamiha disaster happened in 1999.