A plain-language look at the cooling fluid used in our data centers, with the published facts from government and industry sources.
Many modern data centers use a mix of water and propylene glycol to keep computing equipment cool. “Glycol” is an unfamiliar word, and it’s often confused with the toxic antifreeze used in cars. We put together a factual overview of what propylene glycol is and what the science says about its safety for people, pets, and the environment.
Not the antifreeze in your car
Ethylene glycol is the poisonous antifreeze people rightly worry about. Propylene glycol is a different chemical. The U.S. Food and Drug Administration classifies it as Generally Recognized as Safe for use in food, and it’s found in everyday products like salad dressings, medicines, toothpaste, and cosmetics. In cooling systems it’s diluted with water, most commonly as a 25% blend known as “PG25.”
Safe for people
Propylene glycol has very low toxicity. The body breaks it down and clears it much like a food, and it is not a cancer-causing agent. Workers use standard gloves and eye protection as a precaution.
Far safer for pets
Unlike automotive antifreeze, propylene glycol is not a poisoning emergency for animals, and it’s permitted as an ingredient in dog food. Cats are the exception. They’re sensitive to it, which is why it isn’t allowed in cat food, and why any spill is contained and cleaned up.
Gentle on the environment
Propylene glycol is readily biodegradable, doesn’t build up in wildlife, and has low toxicity to aquatic life. The main consideration is volume, not poison: large releases can reduce oxygen in water as microbes break it down. Standard containment and proper disposal prevent that.
The industry standard
PG25 is the coolant the data center industry has standardized on, and it aligns with ASHRAE technical standards. The Open Compute Project, Meta, Dell, and Schneider Electric have all published guidance or documentation on propylene glycol cooling. It’s the same fluid the world’s largest computing operators already rely on.
