Cover graphic by KnackDaily.
Keep dry ice in a thick insulated cooler with the lid resting on loosely, in a well ventilated space, and never in a sealed container or a freezer. It is frozen carbon dioxide at roughly 109 degrees below zero Fahrenheit, and it turns straight into gas as it warms.
Dry ice does not melt, it disappears
Ordinary ice becomes water. Dry ice skips the liquid stage entirely and goes from solid to carbon dioxide gas, a process called sublimation. That single fact drives every rule around it. There is no puddle to mop up, but there is a steady stream of gas coming off the block for as long as you own it.
It also means dry ice cannot be stockpiled. Even in a good cooler a block shrinks noticeably every day, and a thin slab goes faster than a thick one. Buy it close to when you need it and ask the supplier what loss rate they see with their product, since that depends on how it was made and how you are carrying it.
Two rules that matter more than the rest
The first is never seal it. As the solid becomes gas it expands enormously, and a closed jar, bottle, thermos or hard sided case simply builds pressure until it bursts. Coolers are fine precisely because their lids are loose and leaky. Rest the lid on, do not clamp it, and never tape it shut.
The second is never store it in a small closed room. Carbon dioxide is heavier than air, so it pools low in basements, closets, cars and chest freezers rather than dispersing. In a sealed space that displaces the air you need to breathe, and the early warning signs are headache, rapid breathing and confusion rather than any smell. A garage with the door cracked, or an open porch, is the right kind of spot.
The same rule applies to the drive home. Put the cooler in the trunk or the cargo area rather than the passenger footwell, keep a window open, and do not leave it in a parked car.
Where to put the cooler
- Use the thickest walled cooler you have. A cheap foam box works, but the block shrinks faster inside it.
- Fill the empty space with crumpled newspaper or towels. Air gaps speed up sublimation more than people expect.
- Set the cooler on a surface you do not mind, since dry ice can crack tile and damage a countertop on contact.
- Keep it in a ventilated, out of the way place where nobody will trip over it or sit next to it for long.
- Keep children and pets away from it, and tell anyone in the house what is in the cooler.
Handling it without hurting yourself
Bare skin sticks to dry ice and the contact injury behaves like a burn. Use insulated gloves or an oven mitt, or grip it with tongs, and never carry a block against your body. Wrap it in a towel if you need to break a piece off, and break it outside where the gas can escape.
Never put dry ice in a drink someone might swallow, and never place a piece in the mouth. A pellet dropped into a glass for fog should be kept out of reach of the straw, and the safer version is to set the glass inside a bowl of dry ice and water instead.
If skin does get frozen, treat it the way you would treat a burn, and get medical attention when the skin blisters, changes color, or stays numb.
Common mistakes and how to tell it is gone
The mistakes cluster in a few places. People put dry ice in the freezer to save it, which is the worst spot in the house. They wrap it in plastic wrap or a zip bag to stop the fog, which just makes a pressure vessel. They store it in the back seat with the windows up. And they pour water over the remainder to speed disposal, which produces a sudden rush of gas in whatever room they are standing in.
Telling when it is finished is easy. The block shrinks, the fog thins out and then stops, and the cooler contents start warming. There is no residue, no drip and nothing to throw away, which is exactly why it is the tool of choice for shipping frozen goods and for a camping trip that runs longer than a bag of wet ice.
