The increased use of liquid nitrogen in biomedical research in recent years has unfortunately resulted in two fatal incidents in research institutions in Australia and the UK. Some recent incidents that occurred this year at Monash University have highlighted the need for all departments/schools/centres that use liquid nitrogen to review their usage, storage and safety management systems.
Liquid nitrogen is a cryogenic liquid and the hazards associated with it arise from either its very low temperature, the nature of the gas evolved when it boils or a combination of these as detailed below.
|Characteristics of liquid nitrogen||Associated Hazards|
|1. Absence of warning properties
||Asphyxiation - People cannot detect nitrogen in the air as it is
|2. Large expansion ratio on evaporation
||Asphyxiation - Only a relatively small volume of liquid nitrogen has to evaporate within a room to result in an oxygen deficient atmosphere.
Pressure build up &/or explosion - Pressure can build up in a sealed container due to the boil off of nitrogen gas. An explosion can occur if the container is not rated to withstand the pressure.
|3. Low temperature
||Cold burns and frostbite - Cold burns or frostbite can result from direct contact with the liquid. (Note: Storage &/or evaporation of very large volumes of liquid could drop the local atmospheric temperature low enough to cause frostbite or hypothermia. This type of incident is unlikely at Monash )
Increased risk of splashes caused by temperature differentials - There is a high risk of jets or spurts of liquid nitrogen occurring when items, at much higher temperatures than -196 °C, are placed in liquid nitrogen. Pockets of nitrogen gas are formed below the surface of the liquid and can rise rapidly, carrying a jet of liquid with them.
Fire/explosion in an oxygen enriched atmosphere - An oxygen rich atmosphere can result from either condensation or evaporation of liquid oxygen. An oxygen rich atmosphere increases the risk of fire. An explosion may even occur if the evaporation of the liquid oxygen occurs in the presence of organic material (eg cold traps on vacuum lines).
These examples highlight the need for all departments/schools/centres to ensure that they have safe systems in place for the use, storage and management of liquid nitrogen.
i. Incident in February 2003
How was the incident managed?
ii. Incident in July 2003
How was the incident managed?
iii Fatality in Australia in 2001
In December 2001, a staff member at Australian Animal Health Laboratories in Geelong died after entering a room filled with nitrogen gas. The room was used for the storage of samples in cabinets containing liquid nitrogen. Under normal operation, the gas produced by liquid nitrogen evaporation is removed from the room by an exhaust ventilation system. The ventilation system failed due to a series of failures of the laboratory's complex engineering and control systems and the room filled with nitrogen gas. These failures, coupled with inadequacies in relation to staff being alerted to, and understanding the seriousness of, the failures led to the tragedy.
iv. Fatality in research facility in the UK in 1999
In 1999, a fatality involving use of liquid nitrogen occurred at the Human Genetics Unit, located at the Western General Hospital in Edinburgh. Four other people were also injured during this incident. An experienced laboratory worker, who had worked with liquid nitrogen over a period of years, died whilst filling flasks with liquid nitrogen. Seven hundred litres leaked into the laboratory and evaporated, asphyxiating him. A colleague, who entered the room to investigate a hissing noise, which was due to liquid nitrogen streaming from a hose attached to the wall, was able to turn off the supply and summon help before she too was overcome. Three other people were injured during this incident
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