Standard Operating Procedure for:
Refilling 25L L.N. Dewar / PPE required:




Introduction
Exposure of skin to liquid nitrogen (−196 °C) results in cryogenic burns, which have similar symptoms to heat burns. Care must be taken to avoid skin contact or spills of liquid nitrogen.DO NOT attempt to handle liquid nitrogen before being trained by a named colleague.Protective clothing must be worn, including impermeable insulating gloves with an elasticated cuff, a full-face visor, lab coat (closed), and impermeable non-canvas shoes which cover the whole foot. All exposed skin, including legs, should be covered.
The misuse of liquid nitrogen can lead to hypoxia.Hypoxia is extremely dangerous since it is nearly asymptomatic until blackout occurs. Always handle and store liquid nitrogen in a well-ventilated area. This SOP does not cover the use of pressurised vessels.
TRAINING REQUIRED
Refilling 25L liquid nitrogen Dewar
The transport of the 25L Dewar of liquid nitrogen requires two people. Take the empty (or near empty) Dewar (with trolley) along the red route (L10) corridor using the lifts.FullPPE should be carried in case of emergency but should not be worn on the corridors.
  1. Make sure Dewar is in good condition; it is labelled, and is clean and dry.
  2. It is forbidden to accompany liquid nitrogen vessels in the lift. You must display a notice forbidding entry prominently, so that people do not enter the lift at intermediate floors. A second person should be waiting at the destination floor to take charge of the vessel.
  3. Leave the vessel at the agreed place in physics for the agreed time then return following the above procedure.
In case of spillage
The volumes in use (<25L) pose a threat of burns (see below) but should not cause hypoxia unless a large volume is spilled or a large storage Dewar fails. In either case:
  1. EVACUATE THE CORRIDOR OR AREA IMMEDIATELY AROUND THE SPILLAGE.
  2. Contact a technician or appropriately trained member of staff.
  3. If it is safe to do so open windows to ventilate the area.
  4. Do not return or let others pass the area for at least 1 hour and only when you are sure it is safe and another person is with you from a safe distance.
First aid
  1. If the causality is unconscious do not approach, ventilate area if safe to do so and contact a technician or seek emergency help (ex. 32222).
  2. If the causality is conscious, and it is safe to do, remove casualty to a safe place and contact a technician or seek emergency help (ex. 32222).
  3. If it is burn do not apply direct heat but warm with tepid water. Move the casualty to a warm place (approx. 22°C) and seek medical attention (ex.32222).
/ Hazard symbols:

Significant hazards:
  • Very cold
  • Low oxygen levels

Hazard phrases (H):
Can it be done out of hours?
Liquid nitrogen should never be handled out of hours unless specific permission has been received.Can be left in a laboratory overnightifin a suitable container.
This SOP is not relevant in the following circumstances:
  1. SOP does not cover specific experimental risk these must be covered by user’s assessments
  2. Any other situation where the procedure may result in harm to yourself or others.

Standard Operating Procedure for:
Handling liquid nitrogen / PPE required:




Exposure of skin to liquid nitrogen (−196 °C) results in cryogenic burns, which have similar symptoms to heat burns. Care must be taken to avoid skin contact or spills of liquid nitrogen.DO NOT attempt to handle liquid nitrogen before being trained by named colleagues.Protective clothing must be worn, including impermeable insulating gloves with an elasticated cuff, a full-face visor, lab coat (closed), and impermeable non-canvas shoes which cover the whole foot. All exposed skin, including legs, should be covered.If volume handled is less than 500ml insulating glove can be replaced by standard nitrile gloves.
The misuse of liquid nitrogen can lead to hypoxia.Hypoxia is extremely dangerous since it is nearly asymptomatic until blackout occurs. Always handle and store liquid nitrogen in a well-ventilated area. This SOP does not cover the use of pressurised vessels.
TRAINING REQUIRED
Transporting liquid nitrogen
Liquid nitrogen should only be transported in specially designed, stainless steel, well labeled, containers. The maximum amount that should be transported by a single person is 5L.
  1. Make sure Dewar is in good condition; it is labelled, and is clean and dry.
  2. Use the stairs for small quantities of liquid nitrogen. If the lift must be used it requires two people and the SOP for 25L Dewar must be followed.
  3. Full PPE (see above) should be worn while transporting liquid nitrogen.Public areas should be avoided.
Transferring liquid nitrogen
Liquid nitrogen should only be transferred to suitable, well labeled, containers. Full PPE is required(see above)when transferred liquid nitrogen from one vessel to another (unless volume is less than 500ml).
  1. Make sure Dewars are in good condition; they are labelled and are clean and dry.
  2. Always place large Dewars of liquid nitrogen on the floor NOT THE BENCH,
  3. Pouring liquid nitrogen or immersing items should be done slowly to minimise boil off and splashing. A stainless steel funnel can be used to reduce spillage.
  4. Only ever fill containers to 90-95%
In case of spillage
The volumes in use (<25L) pose a threat of burns (see below) but should not cause hypoxia unless a large volume is spilled or a large storage Dewar fails. In either case:
  1. EVACUATE THE LABORATORY.
  2. Contact a technician or appropriately trained member of staff,
  3. Do not return for at least 1 hour and only when you are sure it is safe and another person is with you watching from outside.
First aid
  1. If the causality is unconscious do not approach, ventilate area if safe to do so and contact a technician or seek emergency help (ex.32222).
  2. If the causality is conscious, and it is safe to do, remove casualty to a safe place and contact a technician or seek emergency help (ex.32222).
  3. If it is burn do not apply direct heat but warm with tepid water. Move the casualty to a warm place (approx. 22°C) and seek medical attention (ex.32222).
/ Hazard symbols:

Significant hazards:
  • Very cold
  • Low oxygen levels

Hazard phrases (H):
Can it be done out of hours?
Liquid nitrogen should never be handled out of hours unless specific permission has been received.Can be left in a laboratory overnightifin a suitable container.
This SOP is not relevant in the following circumstances:
  1. SOP does not cover specific experimental risk these must be covered by user’s assessments
  2. Any other situation where the procedure may result in harm to yourself or others.

Standard Operating Procedure for:
Handling dry ice / PPE required:



Dry ice is solid carbon dioxide at −78.5 °C so can results in cryogenic burns, which have similar symptoms to heat burns. Care must be taken to avoid skin contact. DO NOT attempt to handle dry ice before being trained by named colleagues. Protective clothing must be worn, including insulating gloves, safety specs, and lab coat (closed). All exposed skin, including legs, should be covered.
Always store large amounts of dry ice in suitable insulated containers. When dry ice evaporates it produces large volumes of carbon dioxide gas that is toxic and lethal at a concentration of 2.6%. Dry ice must only be handled in Dewars and insulated containers to reduce the rate of boiling.
TRAINING REQUIRED
Collecting dry ice
Dry ice should only be transported in suitable, well labeled, containers. Take the empty (or near empty) containerto the gas cage with suitable PPE.
  1. Make sure container is in good condition; it is labelled, and is clean and dry.
  2. Ideally you should take the stairs as it is forbidden to accompany dry ice in the lift. If you must use the lift display a notice forbidding entry prominently, so that people do not enter the lift at intermediate floors. A second person should be waiting at the destination floor to take charge of the vessel.
Transferring dry ice
Dry ice should only be transferred to suitable, well labeled, containers. PPE is required(see above)when transferred dry ice from one vessel to another.
  1. Make sure containers are in good condition; they are labelled and are clean and dry.
  2. Always place large containers of dry ice on the floor NOT THE BENCH.
  3. Use the scoop provided and be careful to minimise spillage as this could cause a slip hazard.
In case of spillage
The volumes in use (<100kg) pose a threat of burns (see below) but should not cause asphyxia unless a large volume is spilled or a large storage box fails.Elevated CO2 concentrations cause increased heart rate, “panicky” sensations and general feelings of being unwell. If you experience these symptoms or these is a significant (>10kg) spillage:
  1. EVACUATE THE LABORATORY.
  2. Contact a technician or appropriately trained member of staff.
  3. Do not return for at least 1 hour and only when you are sure it is safe and another person is with you watching from outside.
First aid
  1. If the causality is unconscious do not approach, ventilate area if safe to do so and contact a technician or seek emergency help (ex. 32222).
  2. If the causality is conscious, and it is safe to do, remove casualty to a safe place and contact a technician or seek emergency help (ex. 32222).
  3. If it is burn do not apply direct heat but warm with tepid water. Move the casualty to a warm place (approx. 22°C) and seek medical attention (ex.32222).
/ Hazard symbols:
Significant hazards:
  • Very cold
  • Low oxygen levels
  • High CO2 levels

Hazard phrases (H):
Can it be done out of hours?
Dry ice should never be handled out of hours unless specific permission has been received.Can be left in a laboratory overnightifin a suitable container.
This SOP is not relevant in the following circumstances:
  1. SOP does not cover specific experimental risk these must be covered by user’s assessments
  2. Any other situation where the procedure may result in harm to yourself or others.

Assessed by: Andy Connelly (1/12/2013) Updated by: Andy Connelly (2/6/2014)Version 1