Liquid Nitrogen

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The following is a short, distilled safety brief on the Liquid Nitrogen (LN2) that we have at the space.

We currently have a 50 Litre Dewar in a locked cage on the ground floor, next to the Laser cutter. This space was chosen for its proximity to the loading dock and a series of vents in the rear windows.

It is locked when not in use and is to remain locked when not in use.

Gloves and thermos flasks for transportation are provided.

Everyone who wishes to use LN2 for any purpose should make sure for their safety, and for these around them, that they know how to use LN2 safely.

The following are some important safety points.

  • Rule 0 - Do not be on *icy* fire! (remember, cold things burn too!)
  • Be aware of asphyxiation - One of the greatest dangers of LN2 is asphyxiation. LN2 can displace upto 600 times its own volume when it boils at room temperature (this is why it explodes when in a sealed container). This can lead it to displace all the oxygen in the room, which can lead to a situation where you are asphyxiating in a near pure nitrogen atmosphere without realising it as you can still exhale CO2. Always use LN2 in small quantities, in a large open, ventilated room. See for more information.
  • Wear appropriate clothing - This should be clothing that has long sleeves, tight cuffs and the special cryogenic gloves provided. Do not wear any other kind of gloves or any clothing that has significant folds, creases or places where any splashed liquid could pool. Wear footwear that covers the entire foot, i.e no sandals!
  • Use the unsealed, thermos flasks provided, for the decanting of LN2. DO NOT USE ANY FORM OF SEALED CONTAINER! (It will explode and make a mess of your face or someone elses!)
  • The sheepskin gloves and glasses are only to be used with LN2 and should be returned to the dewar area after use. No using them for welding or angle grinding for example! DO NOT USE ANY OTHER KIND OF GLOVES
  • SLOWLY decant LN2 in the first instance - This allows the spout to cool. The escaping gas will also chill your thermos so be prepared for it to get cold. This is useful as it pre-chills your flask.
  • Allow your thermos to stand for 30 seconds, half full, before filling further. Do not fill completely.
  • Do not carry LN2 very far - The further you carry it, the bigger the risk. Make sure your way is clear and there are no trip hazards. This is a common occurrence at the space at present.
  • Do not touch any exposed metal work on the dewar! - The hose/spout at the top of the dewar can become very cold, and indeed, anything surrounding it.
  • Moving LN2 around the hackspace must be done in an unsealed, thermos flask - Do not, for example, use a mug from the kitchen!
  • Do not allow any LN2 to come into contact with bare skin
  • Lock the cage surrounding the dewar when you have finished
  • If you see anything obviously wrong with the LN2 storage, inform the mailing list and the main IRC hackspace channel.
  • Do not leave any LN2 un-watched at any time
  • Do not carry LN2 in the lift or down the stairs to the basement!

The LN2 should be dispensed using the dispenser hose. This is left UNATTACHED. To attach it:

  • remove the temporary bung
  • use the Alankey provided to tighten the bolts.
  • Check the valve on the lid is working and not jammed!
  • Tip the dewar slightly to one side to increase the pressure slightly
  • When you are finished, replace the bung

Most of these are perhaps obvious, but its worth bearing them all in mind before you use any LN2.