We’re frequently asked about the correct personal protective equipment (PPE) that’s required to be worn by operators who are either handling, storing or using liquid nitrogen. Our first response is – ‘have you done a risk assessment?’
Key Takeaways
- A risk assessment must always precede PPE selection for liquid nitrogen use.
- PPE is the last resort in the hierarchy of safety controls.
- The type and amount of exposure will influence PPE choice.
- Gloves, footwear, and face protection must be carefully selected for cryogenic hazards.
- Involve staff in PPE decisions to encourage proper usage.
- Consider portable oxygen monitors in oxygen-deficient environments.
- Poor decanting practices increase the risk of incidents.
Different Tasks, Different Risks
Some of our clients use very small volumes of liquid nitrogen for things like cryosurgery while others use very large quantities for big shrink fitting operations.
So, there are different PPE requirements for differing products, for different tasks, for different situations and for different personnel.
Start with a Risk Assessment
Before undertaking any activity that requires liquid nitrogen you must undertake a risk assessment. As part of this risk assessment you should decide whether PPE is needed.
Use the Hierarchy of Controls
It’s recommended that organisations use what is known as ‘the hierarchy of controls’ to make this decision. PPE should be the last resort to protect against risks. Organisations should consider controls in the following order, with elimination being the most effective and PPE being the least effective:
- Elimination – Do you really need to use liquid nitrogen?
- Substitution – Can you use another process or product?
- Engineering controls – Can you isolate people from the hazards posed by cryogenics?
- Administrative controls – Can you change the way people work with liquid nitrogen?
- PPE – What PPE do you need to protect operators who use liquid nitrogen?
Selecting and Using PPE Effectively
You must select PPE carefully and ensure that all operators are trained to use it properly and know how to detect and report any faults. Before you choose what PPE to buy, think about:
- Who is exposed to liquid nitrogen?
- What are they exposed to? The liquid itself or cold vapour… or both?
- How long are they exposed to the cold liquid or vapour?
- How much liquid nitrogen or cold vapour are they exposed to?
It’s a very good idea to involve staff when selecting PPE as they will be more likely to understand its importance and use it.
Ensuring the PPE Fits the Person
You must select PPE that suits the operator, considering the size, fit and compatibility. This is especially important when selecting cryogenic gloves as not everyone has the same size hands.
Don’t Overlook Oxygen Monitoring
Many of our clients who use liquid nitrogen only consider how to protect the face, hands and feet from liquid nitrogen and cold vapours. When conducting the risk assessment, they should also consider the wearing of portable oxygen monitors that will alert operators to the presence of an oxygen depleted atmosphere.
Head, Face and Eye Protection Considerations
With respect to protecting the head, face and eyes from liquid splashing, spraying or a pressure release, thought should be given to:
- What direction will the liquid travel? Are you simply pouring downwards?
- The fact that safety glasses will only provide a limited level of protection to the eyes.
- The fact that goggles will provide protection to the eyes but not the face.
- The use of a face shield that will protect the whole face but may allow splashes to come under the visor.
In our experience a combination of the above may need to be considered.
Cryogenic Hand Protection
Hand protection must be suitable for the task so that it provides protection, thermal insulation, water resistance and dexterity. Codes of Practice state that non-absorbent leather gloves should always be worn when handling anything that is, or has been recently, in contact with cryogenic liquids.
The gloves should be a loose fit so that they can easily be removed if liquid should splash onto or into them. Gauntlet gloves are not recommended because liquid can easily splash into the wide cuff. Consideration should be given to gloves with elasticated wrists that would stop liquid entering the glove.
It is advisable that gloves conform to BS EN 511, which provides a standard for use in cold environments, but only down to temperatures of minus 20 degrees C.
Protecting the Feet
The feet obviously need to be protected from the cold, spillages, slippage and mechanical impact. Foot protection must be suitable for the task and as well as being comfortable to wear must provide protection against liquid soaking and penetrating the outer footwear, for example, through the material, through openings (such as lace holes), or from travelling down the leg.
On our cryogenic gas workshops we ask staff to consider wearing safety boots with the ‘tongue’ sewn onto the boot so that only a minimal volume of liquid could leak into the boot.
Review Your Working Practices
We frequently find operators who are decanting liquid nitrogen incorrectly from low pressure vessels into working flasks. These poor working practices increase the hazards posed by liquid nitrogen and the likelihood of an incident occurring. Please review your working practices, your method statements and staff training records.
If you require any assistance regarding the safe use of liquid nitrogen then please contact us 01270 758890 or email us at admin@gassafeconsultants.co.uk.
