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What is a dewar?

A dewar is a super insulating vessel for storage of cryogens such as liquid nitrogen, the dewar is double walled with vacuum insulation between the two walls. This vacuum insulation minimises heat transfer to the liquid nitrogen which would otherwise quickly evaporate from its liquid state at -196°C.

Where should I store my dewar?

Wherever possible, all liquid nitrogen containers should be stored externally in on open, well-ventilated position that is at, or above, ground level and sheltered from rain. Always store the container with the protective cap, cover or liquid withdrawal device in place to prevent any moisture or foreign material entering the container.

For Cryosurgery, why does my facility need a qualified medical practitioner or chiropodist?

Air Products considers safety above anything, in cryosurgery or cryotherapy where the intention is for liquid nitrogen vapour to come into direct contact with a patient Air Products insists that the facility has a qualified medical practitioner or chiropodist onsite. This is to ensure that a qualified person is available to assess any potential side effects and if necessary, provide after care.

Why doesn't standard pricing apply in my region?

We want to keep our pricing competitive and though our delivery fleet is located across the United Kingdom, deliveries to some locations incur much higher costs, which unfortunately we need to pass on to customers in these locations. This applies to the following locations; Northern Ireland or one of the following postcodes, KW - Kirkwall, IV - Inverness, AB -Aberdeen, PH - Perth, PA - Paisley, FK – Falkirk. If you are located in one of these regions, please contact for pricing.

Are liquid nitrogen handling training courses available for my staff?

Yes, we partner with a reputable online training company, courses can be quickly completed online. A pass certificate will be issued at the end of the course, successful completion requires correctly answering a series of questions on the course content.

What Personal Protective equipment (PPE) is necessary for handling Liquid Nitrogen?

When handling liquid nitrogen or vessels containing liquid nitrogen, we recommend the following PPE is used at all times:

  • Eye protection, goggles or full-face visor to protect against splashes or pressure releases.
  • Hand protection, non-absorbent, insulated safety gloves that closely fit around the wrist are recommended to protect against possible cold burns from splashes or equipment.
  • Body protection, all parts of the body should be covered when handling liquid nitrogen, long sleeves and trousers should be worn.
  • Foot protection, safety shoes with reinforced toe protection is recommended, open footwear such as sandals must not be worn.
  • Oxygen depletion monitor, we always recommend storing liquid nitrogen dewars outside, however if they are stored indoors the room, or individuals accessing it, should have an oxygen depletion monitor.

Most PPE can be sourced from Air Products directly or via third party suppliers.


Why doesn’t my discharge device work?

Liquid nitrogen will naturally evaporate, even from a super insulated dewar, nitrogen expands by 600 times in volume from the liquid to gaseous phase, this causes a pressure increase in any vessel and is why dewar lids are loose fitting, to allow for this additional pressure to vent. When a discharge device is fitted, there is a pressure valve which will allow excess pressure within the dewar to vent, but an increase in pressure is required for the discharge device to function. Once fitted it can take up to 3 hours for the necessary pressure build up to occur. For this reason, discharge devices should be fitted at least 3 hours before their intended use. If you still find that the device isn't working, check that it is seated correctly as this may be preventing the required pressure build up.

The discharge device also has a manual release pressure valve, if this has been released, either intentionally or accidentally you will have to wait again for the pressure to increase within the dewar before the discharge device will be operable again. If required, further technical advice is available on 0800 389 0202.