Refrigerant and Cold Contact Burns

Why this matters

Liquid refrigerant escaping to open air boils instantly, and to boil it pulls heat out of whatever it touches. On skin that happens in a second or two, and the result is a frostbite injury that can be deeper than it looks, delivered in July, on a technician who was holding a hose fitting. The same injury comes from cryogenic and very cold sources other trades use: a pipe-freezing kit, dry ice, a liquid nitrogen dewar. The first aid is not the first aid for a heat burn. Running a frozen finger under cool water for ten minutes, the right answer for a solder burn, keeps cooling tissue that needs warming.

This card covers cold contact injury from refrigerants and cryogens. Frostbite from weather exposure belongs to its own card. See related: Cold Stress, Frostbite, and Hypothermia. The guidance follows the American Red Cross and the first-aid sections of refrigerant safety data sheets. It is not training: hands-on first aid certification is what makes a responder.

What the cold actually does

At atmospheric pressure, common refrigerants boil far below zero Fahrenheit: R-22 at about minus 41 F, R-410A at about minus 55 F and R-32 at about minus 61 F. Dry ice sits at about minus 109 F and liquid nitrogen at about minus 320 F. Check the SDS (safety data sheet) for the exact figure for anything else. When liquid at those temperatures reaches skin:

• Tissue freezes. Ice crystals form in and between cells, and blood vessels in the area constrict and can be damaged.
• The skin goes white, gray or waxy, and numb. Numbness is the trap: it hurts briefly, then stops, and the person thinks it is over.
• Damage shows up later. Redness, swelling and blistering appear over hours as the tissue thaws, and the depth is often not clear for a day or more.

Two things make it worse than a brief splash should be. Cloth or knit gloves soak up liquid refrigerant and hold it against the skin while it boils off, turning a one-second splash into a long contact. And touching a very cold metal surface, a frozen pipe-freeze jacket or a cylinder valve that has been venting, can freeze moist skin to the metal.

Cryogens carry a second hazard in the truck. Dry ice and liquid nitrogen turn into carbon dioxide and nitrogen gas as they warm, and both displace oxygen. A cooler of dry ice or a leaking dewar riding in a closed van cab can drop the oxygen level enough to make the driver dizzy or confused with no warning smell. Carry them in a ventilated cargo area, never in the cab, and treat a person found confused near either as an inhalation case first.

First, deal with the release

The person who was sprayed is standing next to whatever sprayed them, and the release may still be going:

• Step back from the leak and close the source if it can be closed from outside the spray: the cylinder valve, the manifold valve, the service valve with a gloved hand and a wrench at arm's length. If it cannot, get everyone clear of it.
• Ventilate an enclosed space. Refrigerant vapor is heavier than air and displaces oxygen in a basement, crawlspace or closet. Someone who is dizzy, confused or short of breath after a release in a small space has an inhalation problem as well as a cold burn, and some refrigerants can disturb the heart's rhythm when inhaled at high concentrations. Get them into fresh air and see related: Inhalation Exposure First Response.
• No flame and nothing hot near the release. Many newer refrigerants are mildly flammable (classed A2L), and most halocarbon refrigerants on a flame or a hot surface break down into toxic, corrosive gases including hydrogen fluoride. If a torch was lit for brazing, it is shut off at the valves.

The first aid for the cold burn

Remove soaked gloves, clothing and jewelry, unless they are frozen to the skin. A wet glove is still freezing the hand. Anything frozen to the skin stays where it is until it thaws with the skin under it; tearing it off tears skin.

Rewarm the area in warm water, not hot. Immerse it in water that is comfortably warm to an uninjured hand, about 100 to 105 F, the range the Red Cross gives for rewarming frostbite. Most HVAC techs carry a probe thermometer; use it. Hotter water burns skin that cannot feel heat. Keep the water warm, replacing it as it cools, and keep the part in until color and feeling return, which for frostbite commonly takes 20 to 30 minutes. A brief, light splash that leaves only pink, tingling skin may recover sooner; follow the SDS first-aid section, which for most refrigerants says to thaw with lukewarm water and get medical attention.

Do not rub it, and do not use direct dry heat. Rubbing frozen tissue grinds ice crystals through damaged cells. A heater, a heat gun, a hand dryer, a torch or a van's vent will burn skin that cannot feel it.

Do not thaw if it could refreeze. On a roof in winter or a long walk back to the truck in the cold, thawing and refreezing does more damage than staying frozen for a short time. Protect the area loosely and get to where rewarming can be continuous. That situation is far more common with weather frostbite than refrigerant, but it does come up.

Cover loosely after rewarming with dry, sterile gauze, separating fingers or toes with gauze between them. Do not break blisters.

Eyes. Liquid refrigerant or a cryogen in the eye is an emergency. Flush gently with lukewarm water for at least 15 minutes and go to the emergency department. See related: How to Flush an Eye After a Chemical Splash.

Which cold burns need medical care

A cold injury needs a clinician the same day when any of these is true:

• Blisters form during or after rewarming, or the skin stays white, gray or hard after rewarming.
• Feeling does not return fully after rewarming.
• The area is larger than a fingertip or two, or it is on the face.
• Any eye contact at all, which goes to the emergency department.
• Any inhalation symptoms: dizziness, confusion, irregular heartbeat, chest discomfort or trouble breathing, which is a 911 call.

A splash that left pink, tingling skin which returned fully to normal with rewarming and never blistered can be watched, reported and checked again the next day. Report it regardless, because the shop wants to know which fitting or practice is spraying people.

A worked case: the liquid-line hose

A technician is finishing a charge on a running R-410A system, standing at the outdoor unit in the side yard. He disconnects his liquid-side hose from the service port. The hose's fitting is not a low-loss type, so a burst of liquid refrigerant spits from it onto the fingers of his left hand. He is wearing knit work gloves.

The release. His partner, working nearby, sees the frost on the glove. The burst has stopped; the service port's valve core has closed. There is nothing to close and the yard is open air, so no ventilation problem. Neither has a torch lit.

First minute. The partner gets the knit glove off, which takes a few seconds because it is stiff but not stuck to the skin. The index and middle fingertips are white and waxy, and the tech says they have gone numb. Without the partner, the instinct would have been to shake the hand, rub it on his pants, and keep working.

Rewarming. With the homeowner's permission, the partner fills a bucket at the laundry sink, mixing hot and cold until his probe thermometer reads 102 F, within the 100 to 105 F range. The tech holds his hand in it. The partner checks the water every few minutes and tops it up when it drifts below 100 F. The fingertips go from white to red and start to throb at about 15 minutes, which is a sign of rewarming, not of harm. Feeling is back at about 25 minutes.

Reading it afterwards. By 25 minutes, both fingertips are red and swollen, and a small blister is rising on the index finger. That meets the first criterion in the list above, blisters after rewarming, so the partner covers the hand loosely with gauze between the fingers and drives him to the emergency department, taking the refrigerant's SDS on his phone. The ER confirms a superficial cold injury with a blister, dresses it and releases him.

What changes the answer. If the skin had come back fully to normal by the end of rewarming with no blister, the tech would have reported it, watched it overnight and had it looked at only if blistering appeared. If the release had been in a closet air handler with the tech dizzy afterwards, the first move would have been fresh air and the call would have been 911, with the cold burn second. If the spray had reached his eye, flushing would have come before anything for the hand.

The failure this case avoids. The knit glove. A dry leather or insulated glove rated for refrigerant work sheds a splash; a knit glove soaked it up and held liquid against two fingertips. The shop's fix was low-loss fittings on every hose set and a glove change.

Prevention in three lines

• Wear safety glasses and refrigerant-rated gloves, leather or insulated, never cloth or knit, whenever connecting or disconnecting hoses or handling cylinders.
• Use low-loss hose fittings, and point any fitting away from your face and body as you break it.
• Treat a pipe-freeze kit's jacket and any dry ice as you would a hot pipe: tools or insulated gloves, not bare skin, and read the kit's manual for its own handling rules.

References

• American Red Cross, current first aid guidance on frostbite and cold injury rewarming.
• Refrigerant manufacturers' safety data sheets, section 4 (first-aid measures) and section 10 (decomposition products).
• ANSI/ASHRAE Standard 34, for refrigerant safety classifications such as A2L.
• See related: Cold Stress, Frostbite, and Hypothermia; Inhalation Exposure First Response.
• See related: How to Flush an Eye After a Chemical Splash; Burns: Thermal, Chemical, and Electrical.