The picture of liquid nitrogen has been glamorized just lately in TV cookery packages by cooks akin to Heston Blumenthal. Nevertheless, whether or not you will use it to make selfmade ice cream or to snap-freeze samples within the lab, liquid nitrogen security is crucial, as this reagent isn’t one thing to idiot round with.
On this article, we spotlight the hazards of liquid nitrogen, talk about the need of applicable liquid nitrogen security coaching, and share our prime ideas for avoiding liquid nitrogen risks within the lab.
Liquid Nitrogen Security: Why is it Vital within the Lab?
Liquid nitrogen (additionally known as LN2) is a cryogenic liquid generally utilized in labs. In biology analysis settings, its main use is for preserving organic supplies akin to tissue samples and cells. It is a crucial software in lots of analysis settings, which implies should you work in a biology lab, you’ll in all probability should deal with liquid nitrogen in some unspecified time in the future.
Sadly, researchers have had life-changing accidents and even misplaced their lives due to accidents involving liquid nitrogen, making it crucial that solely working with this liquid totally appreciates the hazards. [1,2]
Liquid Nitrogen Risks
It’s Extraordinarily Chilly
The boiling level of liquid nitrogen is -196ºC/-321ºF, and it freezes at -210ºC/-346ºF.
Between these values, liquid nitrogen is within the liquid state. The acute chilly of this liquid signifies that contact with naked pores and skin can lead to chilly burns, cell injury, and life-changing accidents akin to retinal detachment in an individual’s eye.
Liquid nitrogen can even trigger widespread supplies akin to plastic, carbon metal, and rubber to fatigue and ultimately fracture.
It’s an Asphyxiant
One of the harmful properties of liquid nitrogen is its potential to boil into massive volumes of fuel.
The liquid-to-gas enlargement ratio is 1:694 at 20ºC/68ºF.
This implies 1 L of liquid nitrogen can increase to 694 L of fuel.  If sufficient liquid boils in a confined house, the air may be displaced, leading to an oxygen deficiency.
The lowered oxygen focus can rapidly lead to feeling dizzy and render you unconscious with little warning, as nitrogen fuel is colorless, odorless, and tasteless.
The best way to Calculate Proportion Oxygen Depletion Incase of Dewar Failure
Questioning how a lot oxygen would get displaced if the liquid nitrogen Dewar in your lab failed whereas full? Have to know this calculation in your threat assessments? Right here’s methods to work it out.
Air is 21% oxygen and 78% nitrogen.
Typically talking, we shouldn’t enter rooms containing lower than 20% oxygen. Oxygen depletion alarms normally sound at 19.5%, and a few two-stage alarms sound once more at 18%.
We are able to use the enlargement ratio of LN2 and the quantity of a lab to calculate how a lot the atmospheric oxygen proportion would stay after a spillage.
The equation we’d like is:
%O2 remaining = 100 x (21 x [ Volumeroom – Volumereleased gas ]) / [ Volumeroom ]
And because it’s helpful to maintain all items in meters, m:
1 L = 0.001 m3
Let’s think about a state of affairs through which a 25 L Dewar of liquid nitrogen fails in a 300 m3 lab. How a lot oxygen would stay? If 1L of liquid nitrogen produces 694 L of fuel, 25 L of liquid produces 17,350 L of fuel. In meters cubed, that’s 17,350/1000 = 17.35 m3.
Subbing into our equitation, we get:
100 x (21 x [ 300 – 17.35 ]) / 300 = 19.79%
So it wouldn’t journey the oxygen depletion alarm, nevertheless it’s shut. Now think about how small a raise is. By no means journey in a raise with liquid nitrogen. If it’s worthwhile to transport it between flooring, ship the Dewar within the raise and take the steps.
Additionally, for this reason areas the place liquid nitrogen is saved and dealt with ought to have applicable oxygen sensors that alarm when the oxygen focus falls.
It Can Trigger Explosions
The big enlargement ratio additionally signifies that if liquid nitrogen boils in a confined house with no escape, the strain buildup can lead to an explosion. Subsequently, liquid nitrogen storage gear ought to have applicable pressure-relief units.
High Suggestions for Security Dealing with Liquid Nitrogen
Now you recognize the hazards of liquid nitrogen, let’s have a look at how one can deal with it safely within the lab.
1. Get Correct Liquid Nitrogen Security Coaching
Earlier than you begin work with liquid nitrogen within the lab, whether or not it’s utilizing a Dewar flask for flash-freezing or putting your cells in for cryo-storage, it’s worthwhile to get correct security coaching.
Converse to your supervisor or lab security supervisor—they need to present applicable coaching, together with on PPE, protected dealing with, and what to do in an emergency.
The potential risks of liquid nitrogen imply it’s best to get some primary security coaching if utilized in the identical space you’re employed in, even should you aren’t straight working with it.
2. Know The best way to Retailer and Transport Liquid Nitrogen
The storage of liquid nitrogen containers is extremely regulated. There are particular well being and security necessities that require good air flow and restrict the variety of storage containers in a single room. Be sure you are accustomed to your institute’s insurance policies.
When aliquoting a smaller quantity to be used in a laboratory process, solely use a container specified for liquid nitrogen. Don’t use a home vacuum flask or any previous container hanging across the lab. Uninsulated containers can freeze to pores and skin and tear it when eliminated. Unsuitable containers can even all of the sudden crack and spill liquid nitrogen all over the place.
3. Put on Applicable Private Protecting Tools
When utilizing liquid nitrogen, you need to defend your pores and skin, significantly your face and eyes, from splashes. Subsequently, it’s worthwhile to put on private protecting gear (PPE), together with a lab coat, specialised gloves, and goggles.
Be aware that relying on the kind of gloves you employ, you might solely be shielded from the extraordinarily low temperatures of saved objects, not from direct publicity to liquid nitrogen, so don’t submerge your palms.
Whereas small splashes of liquid nitrogen might not trigger a burn, due to the Leidenfrost impact,  if allowed to pool, liquid nitrogen may cause extreme burns.
So concentrate on liquid nitrogen getting down the cuffs of your gloves!
For added safety, you must also contemplate sporting goggles beneath a full-face defend. I’ve heard of circumstances the place folks have been splashed within the eye when organizing cryotubes in a Dewar, regardless of having a full-face defend. The stuff can shoot up from all angles!
Additionally, it’s best to be certain that your footwear doesn’t depart any uncovered areas, or else you may find yourself with frostbitten toes.
4. Work in a Properly-Ventilated Space and Keep away from Confined Areas
As mentioned within the above part on liquid nitrogen risks, asphyxiation is an actual threat. Guarantee any space you’re working in with liquid nitrogen is well-ventilated, keep away from confined areas akin to elevators and monitor oxygen ranges.
If this will’t be prevented, communicate to your lab security supervisor in regards to the crucial steps to make sure that dangers are appropriately managed, akin to not permitting others to trip within the elevator and making certain a colleague is conscious.
5. Do Not Work with Liquid Nitrogen When You might be Alone within the Lab or After Hours
When working with liquid nitrogen, significantly when allotting from a big to a small container, ensure that a colleague is close by and is conscious of what you’re doing. The significance of that is highlighted by the tragic loss of life of a researcher working alone. 
6. Use Solely the Obligatory Quantity of Liquid Nitrogen
The big enlargement quantity of liquid nitrogen signifies that it’s best to restrict the quantity you employ and deal with to the minimal you want. Utilizing extreme quantities can dramatically enhance the danger of asphyxiation.
7. Don’t Go Diving right into a Storage Container to Retrieve a Dropped Pattern
No pattern is value asphyxiating your self from the vapors or burning your face and palms when the liquid bubbles up.
8. By no means Use Liquid Nitrogen in a Closed Container
Liquid nitrogen boils quickly and might trigger ice dams to kind or strain to construct up, leading to explosions. Guarantee storage containers are correctly vented, and by no means use liquid nitrogen in a closed system.
9. By no means Put Liquid Nitrogen Down the Sink
It may possibly trigger the pipes to crack, and you should have an costly restore invoice. Moreover, liquid nitrogen poured down one drain can come up one other, which might be a nasty shock for a colleague within the lab subsequent door.
10. Watch Out for Exploding Cryotubes
Cryotubes needs to be protected for liquid nitrogen, proper? Not at all times. Liquid nitrogen can unknowingly enter cryotubes by way of minute cracks and increase rapidly when the tube thaws. An exploding cryotube may be like a mini-missile, and a former colleague of mine has a mark on her brow to show it!
Liquid Nitrogen Security within the Lab Summarized
Liquid nitrogen security is essential when working within the lab. In case you or others in your lab are working with liquid nitrogen, guarantee you’ve got the suitable liquid nitrogen security coaching.
Some key concerns to keep away from the potential risks of liquid nitrogen embody working in a well-ventilated space and monitoring oxygen ranges if working with massive quantities.
By no means work with liquid nitrogen alone or out of hours in case of emergencies. Put on applicable PPE to reduce the danger of chilly burns and different liquid nitrogen-related accidents. Use applicable storage containers to forestall explosions from strain build-up or leaks from broken containers.
Do you’ve got some other ideas for liquid nitrogen security? Go away a remark beneath in that case.
Initially revealed 6 January 2014. Reviewed and up to date November 2021. Reviewed and up to date once more December 2022.
- Tristan Kirk. Imperial Faculty London fined £70,000 after scientist suffocated in lab crammed with nitrogen. Night Customary. 13 December 2017
- Security issues led to lab loss of life. BBC Information. 20 June 2000
- Liquid nitrogen. Wikipedia. Accessed 16 November 2021