Six people have died and another eleven were hospitalised following a liquid nitrogen spill at a Chicken processing plant in Gainssville, Georgia, on Thursday 28 January 2021. Three of those who were injured were described as being in serious conditions after the incident, while four were firefighters from Hall County Fire Services and Gainesville Fire who attended the incident, which was caused when a pipe supplying liquid nitrogen to a refrigeration plant ruptured.
Nitrogen has a boiling point of -196°C, which means that liquid nitrogen at standard pressures will always be at least this cold. Liquids at this temperature are, obviously, somewhat dangerous, and can cause freeze burns to the flesh. However, it takes relatively little energy to vaporise liquid nitrogen (which is generally at boiling point when spilled anyway), with the effect that liquid nitrogen spilt on the skin quickly vaporises, often doing little damage, although if the liquid becomes trapped inside clothing or shoes, which hamper its dispersal, then it is more dangerous, and metal object which have come into contact with liquid nitrogen are more hazardous. The main danger associated with liquid nitrogen is, however, its ability to displace oxygen as it vaporises. An equivalent mass of gaseous nitrogen occupies 683 times as much space as liquid nitrogen (i.e. one cubic metre of liquid nitrogen will occupy 683 cubic metres once it has vapourised). As nitrogen is an asphyxiant (i.e. we can't breath it) this makes liquid nitrogen spills in enclosed spaces extremely dangerous, particularly as the Human body neither detects nitrogen (which makes up about 80% of the atmosphere anyway), nor the absence of oxygen (the feeling of being unable to breath that we sometimes get is caused by the body detecting raised levels of carbon dioxide), with the effect that people exposed to high nitrogen, low oxygen atmospheres tend to collapse without warning (although places where this is likely to be possible can, and should, be fitted with oxygen sensors that detect the drop in breathable atmosphere, triggering an alarm).
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