How To Use Liquid Nitrogen

Treatment and storage of liquid nitrogen

May 2021

This information sheet provides advice for developing, maintaining and implementing local safe work practices for all workers at the university who are required to use liquid nitrogen. Liquid nitrogen is commonly used across Monash University for the purposes of snap-freezing and long-term storage of biological samples and in cold traps on vacuum lines/equipment

1. What is liquid nitrogen?

LN₂ (liquid nitrogen) is a cryogenic liquid and is the liquefied form of nitrogen gas at atmospheric pressure and subzero temperature. Its backdrop are listed in the post-obit tabular array.

Dangerous goods class
Boiling point (°C)	-196
Color of gas	None
Odour of gas	None
Taste of gas	None
Expansion ratio	790×
Gas density (27°C air = i·18g/Fifty)	ane·14

2. Hazards associated with Liquid Nitrogen

Asphyxiation

When LN2 boils it produces gaseous nitrogen, which displaces oxygen from the air. This results in an oxygen-deficient atmosphere, specially if vented into a closed space, and asphyxia can result.

The wellness effects of diminished oxygen in the environment can exist acute and the impact severe as detailed below.

O₂ > 19·5%	Normal role
14% < O_two ≤ 19·5%	Diminution of physical and intellectual performance without person's noesis
O₂ ≤ 14%	Fainting, unconsciousness, decease depending on level and duration without adequate oxygen

Common cold burns

Due to its extremely low temperature, the cold vapour and gas that are produced when LN₂ boils can requite rise to common cold burns or frostbite upon contact with unprotected peel. Exposure may also produce discomfort in breathing and can provoke an asthma attack in susceptible individuals.

Fire in oxygen-enriched atmosphere

LN_ii tin can condense oxygen from the temper. Liquid oxygen creates potentially flammable or explosive conditions by greatly increasing the combustibility of many materials (e.g. solvents, hydrocarbons).

Pressure build-up/Ice plug formation

Due to the large expansion ratio (liquid to gas), if LN_two is evaporating within a closed system, the pressure can build up with a loftier take a chance of explosion. Ice plugs tin can class on the neck of narrow storage vessels if there is no relief vent, every bit h2o is readily condensed past LN₂ to form water ice. This will atomic number 82 to pressure build up in the storage vessel.

3. First help

In no circumstances is it considered safe to enter an oxygen-deprived environment for the purposes of patient rescue.

Asphyxiation	Immediate help should be sought from emergency services past dialling 333 or 0-000 from any internal phone. Once in omnipresence, emergency personnel will manage the state of affairs.
Cold burns	Affluent affected area with tepid or unheated tap water. Use non-stick dressing and seek medical attention. If peel is adhered to a common cold metal surface, run common cold water between the skin and the metal surface, rather than attempting to pull skin away from the surface.

four. Risk management & safe work practices

Risk assessments must be completed past each area where LN₂ is handled and stored using the information detailed in the Safety Data Sheet (SDS) and that which is detailed beneath. It is important to consider the task being performed and the quantities of LN_ii used in social club to select the almost appropriate control measures. Rubber work instructions must then exist adult and control measures implemented and followed.

Storage facilities

The command measures required in facilities used for using and/or storing LN₂ differ depending on the lowest likely oxygen level.

Lowest probable oxygen level (every bit a result of room dimension & volume of LN₂ stored)	Risk command measures (applied science & administrative)
O₂ > 19·5%	Basic requirements: signage written procedures for emergencies displayed windows/grilles partly open at all times water for burns available no common cold rooms or unventilated rooms training for all users no demand to evacuate firsthand area.
14% < O₂ ≤ xix·5%	In addition to the basic requirements: room mechanically ventilated for heating/cooling access controlled glass panel in upper half of door single, audible, visible depression oxygen detector - 1m off floor in room emergency end button for reticulated systems evacuate immediately if incident occurs.
O₂ ≤ 14%	All of the higher up controls required, plus: CCTV cameras no after-hours access evacuate immediately if incident occurs.

Dewars and storage vessels

Storage vessels are classed as force per unit area vessels and must run into the requirements of AS2030.4 They accept an internal volume capacity of ≥ 50L and are used for majority storage. In well-nigh cases, these are leased from the supplier and it is their responsibleness to maintain the storage vessels in accordance with the standard.
Dewars are portable, double walled containers that are open-necked, gratuitous-venting and non-pressurised. Only dewars that run into Equally 1894 should be used and a regular physical inspection should be carried out to check the external surface integrity.

Transport and filling operations

Containers that meet the requirements of AS 1894 must be used when handling modest volumes of LN_two for use in the laboratory, east.yard. for snap freezing of samples. Domestic thermo flasks are not appropriate for this purpose, as they are non designed to be gratuitous-venting and tin issue in pressure build-up and a subsequent explosion.
Only accordingly trained personnel should perform LN_ii filling and transferring tasks. Controls to minimise the likelihood of splashes as well as exposure to escaping liquid/gases must be in place, e.chiliad. using LN_ii pumps and ensuring there is adequate ventilation.
Advisable trolleys must be used for transporting dewars between buildings to ensure that the dewar is secure at all times.
Dewars must never be accompanied in lifts due to the risk of asphyxiation. In areas where dewars demand to exist transported betwixt floors via lift, a articulate procedure must exist in place and available to all staff. Where possible, access to intervening floors should be locked out or the elevator must be clearly sign-posted whilst LN₂ dewars are in transit with a trained member of staff receiving the dewar at the last destination.
For transport between different locations, dewars must exist firmly secured in an open truck, utility or trailer. Alternatively, a cryoporter or dry out shipper can exist used and these are also suitable when samples need to be mailed.

In addition to the engineering and authoritative controls outlined above, appropriate Personal Protective Equipment (PPE) must exist selected and used, based on the principle that it should prevent LN₂ from touching the peel and eyes.

Thermo-insulated gloves (elbow length and loose fitting).
Safety glasses/full face shield.
Long sleeve lab coat.
Apron/Long pants.
Fully enclosed footwear.

Consecration and preparation

All users working with LN_two must complete the online "Cryogenic Material Basic Safety Principles" training in myDevelopment. Users who wish to access LN₂ storage and/or dispensing facilities will need to complete a local area induction. The induction must be recorded using the Local Area Cryogenics Facility Induction checklist and the records maintained locally. The consecration must be delivered by the relevant facility manager or their authorised delegate.

v. References

Australian Dangerous Goods Code for the ship of Dangerous Appurtenances, version 7.7.
AS 1894 (1997): The storage and handling of non-flammable cryogenic & refrigerated liquids.
Equally 2030.4 (1985): The verification, filling, inspection, testing and maintenance of cylinders for the storage & ship of compressed gases.
Using chemicals at Monash (pdf 95kb).
Local Area Cryogenics Facility Induction checklist

6. Farther information

For further information, contact your local OHS Consultant or Occupational Health and Safety:

telephone: 990 51016
due east-mail: ohshelpline@monash.edu