Safety in the Laboratory


Liquid Nitrogen (LN2)


Skin contact with liquid or cold metal cause freezing / frostbites of exposed tissue due to the very low temperature (boiling point: -196 °C)

Eye contact already with vapor may cause a stinging sensation

Risk of asphyxia due to liberating nitrogen (and deplacing oxygen);
as nitrogen is odourless, colourless and tasteless, this may occur without any sensation or prior warning

Risk of explosion due to expansion ratio of 1:694 when heated up
→ never close a container well, which contains LN2

see "SI Liquid Nitrogen"
 Cold

Always use safety glases or better a face protection. Optical glasses are not allowed.

Always use special protective gloves against the cold (Kevlar);
those should be waterproofed that no accidentally spilled liquid nitrogen may enter

Use closed shoes from leather. 		Gloves
face protection

Store Dewars for liquid nitrogen only in well ventilated places and protected against tumble over or breakage

Only use clean and dry Dewars

Do not left Dewars with liquid nitrogen open: oxygen of the air may condense into the liquid nitrogen and accumulate provoking the risk of a combustion in the case of contact with flammable (organic) matter

  
 
  

Cryoconservation

The Dewar for cryoconservation should be located outside of the normal laboratory

Filling up a warm Dewar: Add a small quantity LN2 to cool the Dewar down (~ 2 h) before fill it up

Refill a Dewar: Avoid spilling of LN2 over the vacuum cap near the neck, which would damage the sealing
         resulting in a premature lost of vacuum
       - Do not overfill Dewar with LN2: max. 30 cm for the Chart/MVE XC43/28.

Measure fill level: Enter solid plastic dip stick and remove it: condensing water indicates level
       - Never use a hollow tube, as LN2 will leave at its end

LN2 withdrawal: Use the dipper to transfer LN2 into a small Dewar

Cell storage: Fill into 1.2 ml cryovials 1 ml medium/cells/cryoprotection
       - Transfer vials into "Mr. Frosty" for slow cool down to - 20 °C (better - 80 °C)
       - Clip fastly vials into cane-holder and place this in the canister (colour-code)
       - cryovials should be stored in the vapor phase and not submered in the LN2
         when submerged storage is necessary (e.g. to prolong working range)
         special sealed vials and a cryoshrinktube should be used to avoid the entering of LN2 into the vials

Cell removal: Get off vial from cane - do not expose other vials to ambient temperature
       - When LN2 entered into the vial, the tap can spring off explosively. Use faceshield
       - Thaw up vial to 37 °C in dry bath and change medium to remove cryoprotection

MVE XC-43/28


General construction of a Dewar:

a) Tamper proofed lid

b) Locking tab

c) Easy maintenace lid
,
d) Colour coded lid numbering system

e) High strength neck to reduce nitrogen loss

f) Advanced vacuum system

g) Insulation

h) Superior strength aluminium construction

i) Spider desgin for easy retrival and insertion of canisters


 Dewar
MVE XC 43/28

Number canister: 6

Canister height: 28 cm

Canister diameter: 5.6 cm

Canes/canister: ~ 12

Cryovials/Cane: 5

LN2 [l]: 42

Evaporation/d [l]: 0.14

Working range [d]: 190

Neck diameter [mm]: 70
MVE







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Last modified: 13.12.2009