Working safely with cryogenic gases
29/11/2021
From gas detectors to protective clothing
Cryogenic gases are widely used in laboratories as well as pharmaceutical environments, in the industrial sector, and even in restaurants. Using cryogenic gases offers a number of unique advantages but is not without risk.
Using cryogenic gases incorrectly can lead to the risk of suffocation and third-degree burns. Stefan Suys, Product Manager Equipment and Installations for Air Liquide's North-West Europe Cluster, explains: "Liquid nitrogen - which is the most commonly used cryogenic gas - is odourless and tasteless and, when it evaporates, it can fill a room unnoticed, displacing the oxygen present.”
“It’s important to bear in mind that the volume of liquid nitrogen increases by a factor of x680 when it evaporates. So a dangerous atmosphere can be created if relatively small quantities of nitrogen escape. Gas detectors to monitor oxygen content - worn on the body or installed in rooms where cryogenic gases are used - are therefore absolutely essential."
Cryogenic containers
Cryogenic gases are delivered in specially designed vessels or in large exterior storage tanks. If it is the latter, users have to fill their containers from the tank themselves. Air Liquide has a wide range of containers available for cryogenic gases. These include both hermetically sealed vessels with a pressure build-up system and traditional vessels with a sealing cap. Both variants are available in different sizes, with or without wheels.
"A hermetically sealed vessel with a pressure build-up system is particularly useful because you don't have to pour the cryogenic liquid," says Stefan. "But it’s important to ensure that the pressure in the vessel doesn’t get too high. If it does, the pressure relief valve opens automatically to stop the vessel exploding. But when that happens, a quantity of gaseous nitrogen enters the room.”
“If the user then forgets to close the tap that regulates the pressure build-up, the pressure relief valve will keep opening and the amount of nitrogen in the room will continue to increase. Anyone entering the room would then run a high risk of suffocation, especially if there’s no gas detector. It’s also obligatory to put up warning signs in rooms where cryogenic gases are handled. And finally, having a powerful ventilation system is strongly recommended."
Preventing burns
Traditional vessels do not have a pressure-building system and therefore have to be poured manually. Every time the cap is removed, a small amount of gaseous nitrogen is released, but under normal circumstances this should not cause any problems. Nevertheless, using a gas detector is necessary for these vessels too, to guarantee safety. And that's not all. "If you pour cryogenic nitrogen from a vial, splashes could fall onto the skin, which can cause serious, possibly third-degree burns," Stefan adds. "What’s more, contact with liquid nitrogen doesn’t cause a pain reaction and so there’s no clear signal transmitted by the nervous system.”
“It’s therefore important that users wear the necessary protective equipment. Safety gloves and goggles are a minimum requirement. We also recommend using a face shield and it’s important to wear closed shoes and long-sleeved outer clothing. Items such as safety gloves, safety goggles and face shields are also available from Air Liquide."
Download our white paper on working safely with gases in the lab here.