The Dangers of Cryogenic Burns and How to Prevent Them

Cryogenics have been described as the way of the future. According to Air Liquide, a leading supplier of gases, technologies and services for Industry and Health, the cryogenics industry is where "liquid gases such as nitrogen, carbon dioxide, helium and hydrogen are used as refrigerants to modify the physical properties of materials or to maintain temperature during process steps. They can also be used as an energy source to power various applications such as fuel cell vehicles and microelectronics." There are three different types of cryogenic liquids: inert gas, flammable gas, and oxygen. The Canadian Center for Occupational Health and Safety talk about the differences and how they are contained a bit more in detail. Today is all about the Dangers of Cryogenic Burns and How to Prevent Them.

So why do we need cryogenics? Cryogenic liquids can be found in everyday items like aerosol sprays, engines and refrigerators. Consumers make daily use out of products and services that belong to some part of the cryogenics industry. With the growing need for cryogenics, there also is a need to spread awareness about the potential dangers that occur when these materials are not handled properly. These materials can cause life threatening damage, or even cause death, so learning the hazards and how to safely handle these materials are of the upmost importance.

What are Cryogenic Burns?

Most people know the pain when they touch something too hot, like a hot stovetop or a pan on the oven. But did you know that you can also be burned by touching something that's too cold as well? Study.com explains, "Cryogenic Burns occur when human skin comes into contact with extremely cold, liquified gases".

At room temperature, these elements would normally be in their gaseous state, but under extreme pressure and cooling, they have liquified. "A common example used to demonstrate this in science labs is Liquid Nitrogen, which has a boiling point of 320.4°F. This means that it must be cooled beyond that temperature to become a liquid. Many of these types of liquids boil violently at room temperature as they change back into gases".

Cryogenic burns can also happen by coming into contact with the materials that contain the liquid gases. The metals containers that hold cryogenic fluids can't retain their heat, so they become so cold that upon contact, can cause burns. If bare skin were to come into contact with these metal containers, it could potentially tear skin.

Although severe cryogenic burns are very rare, typically only found in people working with Liquid Nitrogen or industrial coolants, there has been a recent uptick in children burning themselves with aerosol sprays, so we want to share some information about these materials.

Pathophysiology of Cryogenic Burns

In case you want to know the scientific explanation of cryogenic burns, Study.com explains that they are "cold burns, meaning the tissue is damaged from the cold temperature of the liquid. When our cells get too cold, the liquid inside freezes, damaging the structural integrity of the cells." Because the cells are damaged, they don't go back to the way they were when thawed. Once the damage is done, it can be permanent.

"Cryogenic burns are also different from heat or chemical burns. Excessive heat or chemical damage to the skin causes proteins to denature, or break apart." What this means is that the structure of the skin cells falls apart and that leads to scarring. Proteins do not break apart in cryogenic burns, and only really severe cases cause scarring.

Just like the different levels of thermal burns, cryogenic burns also have different intensities. Just like if you were out in the sun too long, the intensity of the burn depends on how much it was exposed to. Longer exposure time can actually cause frostbite where the skin looks waxy and yellow. The tissue turns black, dies, and in extreme cases can lead to amputation.

What are the hazards of Cryogenic Liquids?

In the cryogenics industry, there are three main hazards associated with cryogenic liquids: extreme cold, asphyxiation, and toxicity. Each of these carries their own weight, so let's break them down.

Extreme Cold Hazard

Typically, cryogenic liquids are kept at degrees ranging from -120°C (-185°F) to -195.8°C (-320°F). The reason cryogenics are so harmful is because of the extremely low temperatures, and when these liquefied gases come into contact with human skin, it can cause extreme burns.

The effects of a cryogenics burn are similar to a thermal burn, but if exposed for an extended amount of time, the damage can be severe. Exposure can cause damage to sensitive tissues like the eyes, while not appearing on other areas of skin.

Unprotected skin and tissues can stick to metal and other materials at low temperatures when in contact with the cryogenic liquids as well, which can lead to tearing. The last issue with a prolonged amount of exposure is damage to the lungs. Breathing in these hazardous materials can lead to issues later in life.

Asphyxiation Hazard

When cryogenic liquids form a gas, the gas is very cold and often heavier than air. If we learned anything from science class, we know that dense, cold gas doesn't disperse very well and can accumulate near the floor. Small amounts of liquid can evaporate into a very large volumes of gas. For example, one liter of liquid nitrogen vaporizes to 695 liters of nitrogen gas when warmed. Even if the gas is nontoxic, it still displaces air. When there's not enough oxygen in the air, it can lead to asphyxiation or even death. Oxygen deficiency is a serious hazard, especially in enclosed or confined spaces.

Toxicity Hazard

Last is toxicity. Each gas can have its own health affects. Liquid Carbon Monoxide can produce Carbon Monoxide gas which can cause death almost immediately. A lot of the gases are colorless and odorless as well, making exposure hard to recognize. See here for the full list of affects from the Safety Data Sheet.

With all that said, another thing to take into consideration with cryogenic liquids is the flammability hazards. Several types of situations may result in a flammability hazard including fire, oxygen-enriched air, liquid oxygen and lastly, explosion due to rapid expansion.

Fire Hazard

Some of the gases being transported are flammable by nature like Hydrogen, Methane, Liquefied Natural Gas, and Carbon Monoxide. Of these, Hydrogen is particularly hazardous because as it moves through the air,  it forms flammable mixtures and is very easily ignited.

Oxygen-Enriched Air

Liquid Hydrogen and Liquid Helium are both so cold that they can liquefy the air it comes in contact with. For example, liquid air can condense on a surface cooled by Liquid Hydrogen or Helium. Nitrogen evaporates more quickly than oxygen from the liquid air.

This sudden evaporation leaves behind a liquid air mixture which, when evaporated, leaves behind a large amount of oxygen molecules. This "Oxygen-Enriched" air now has all of the same hazards as Oxygen.

Liquid Oxygen Hazard

Oxygen, if you can't tell, is a very hazardous material as it gets its own section. Liquid Oxygen contains 4,000 times more oxygen by volume than normal air. Liquid Oxygen has the ability to affect materials that are usually considered non-combustible (such as carbon, stainless steel, cast iron, aluminum, zinc, or teflon). Organic materials may react explosively, especially when a flammable mixture is produced as a result. When clothing is in contact with Liquid Oxygen, it will stay highly flammable for hours.

Explosion Due to Rapid Expansion

If the container does not have adequate ventilation or pressure-relieving devices, significant pressures can build up. The pressure can cause an explosion called a 'boiling liquid expanding vapor explosion'; a fancy name for a huge and dangerous explosion. Any unusual or accidental conditions like a a break in the vacuum or a fire can cause a very quick pressure spike. If the pressure relief valve can't handle this pressure increase, the storage containers have to have another backup device such as a frangible (bursting) disc.

How to Prevent Cryogenic Burns

To summarize, cryogenics are dangerous and should not be taken lightly-that's why they're called hazardous materials. So how do you prevent getting a burn?

When loading and unloading Hose Connection and Disconnection:

• Always inspect the trailer and hose fittings for damage to the threads
• Replace gaskets on trailer and customer fittings prior to loading or unloading
• Never loosen hose connections prior to depressurizing hose
• Open drain valve and allow the hose to depressurize
• Always stand to the side when disconnecting hose, slowly and carefully cap the hose and stow it in the trailer hose tube

Burns occur when skin is in direct contact with cryogenic liquids or high-pressure cryogenic vapor, so the correct safety gear will protect you from the hazardous liquids.

Safety Gear to Avoid Direct Contact

• Always wear a hard hat with a full face shield
• Wear safety glasses with side shields or safety goggles
• Hearing protection (ear muffs or plugs) to help limit skin exposure as well as protect your hearing
• Long sleeve shirts or jackets, never wear short sleeves
• This is vital. Wear heavy duty leather gloves with long cuffs for cryogenic liquids or rubber gloves with a wrinkle finish and long cuffs for carbon dioxide
• Have a pair of steel towed safety shoes with a non-skid sole and some fire retardant overalls
• Lastly, have air monitors H2S and O2

If an accident were to occur, First Aid procedures would need to follow.

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First Aid | Cryogenic Burns (Argon, Helium, Nitrogen, Oxygen)[/caption]