Overview
- Are low pressure containers
- Periodic venting to remain cold
- Nitrogen most common; liquid oxygen is more dangerous
- Does NOT include dewars
Cylinders for refrigerated liquified gases contain chemicals called cryogenic liquids because these chemicals are liquids at temperatures below −150 °C (−238 °F). Nitrogen is the most common cryogenic liquid on campus. Unlike compressed or liquified gases, cylinders for cyrogenic liquids are relatively low pressure. This is due to a significant difference between these cylinders and the other types.
Cylinders for cryogenic liquids are designed to vent periodically. The venting serves two purposes. First it reduces pressure in the cylinder and second the venting acts to recool the liquid. Thus, don’t be surprised if you find a cylinder like this ‘leaking.’ This is natural. In most cases though, the venting will be short and it might even be loud enough to be startling.
Cryogenic liquid oxygen is possible. It is exceedingly dangerous. It will ignite combustible materials on contact such as wood. Mixed with combustible liquids, it will spontaneously detonate. Even elevated concentrations in the air is dangerous. Locations where this cyrogen is used are subject to special design considerations to prevent the build up of oxygen in the space. If you find a cryogenic cylinder of oxygen, report it to a Senior Specialist for follow-up.
Dewars are not considered cylinders and will be discussed next.