Why Do CO2 Cartridges Get So Cold?

Q: I have been investigating carrying CO2 cartridges and a CO2 tire inflator in my bike bag, rather than exhausting my arms with a hand pump when I have to inflate on a ride. I keep reading consumer comments about how I should invest in a CO2 tire inflator that “prevents frostbite.” Or one that “stops my fingers from getting frozen.” What are they talking about?

 A: CO2 cartridges are highly compressed cylinders of liquid carbon dioxide. As the liquid CO2 is released, it turns into a gas and makes your cartridge ice cold.

This frost-all-over-the-cylinder sort of cold is thermodynamics in action: Changing from a liquid phase to a gas phase requires energy. As the CO2 is released into the air, it steals the energy required to convert in the form of heat from the metal cartridge casing, making the CO2 cartridge frigidly cold. In short, as the pressure inside the cartridge decreases, so does the temperature.

Thankfully, there are a couple of solutions to combat CO2 cartridge frostbite when inflating your bicycle tires:

No. 1: Select a cupped CO2 tire inflator or inflator head with a sheath designed to protect your fingers. 

Genuine Innovations’ popular Ultraflate CO2 inflator is a good example of a cupped tire inflator that keeps your hands off the cartridge. Its reinforced glass nylon construction makes it durable and reliable. Plus, you can store a non-threaded 20 gram CO2 cartridge in the cup until you are ready to use it!

You are more likely to feel the (CO2) burn if you can’t control the flow of CO2. Some CO2 tire inflators are “all in,” meaning once you pierce the CO2 cartridge, the air is coming out whether you are ready or not. But good bicycle CO2 inflators allow you to control the flow of air. Genuine Innovations actually offers three different types of air flow control technology: Push-to-inflate, twist-to-inflate and trigger controlled (like on the HammerHead CO2 inflator pictured on the right). Select the option that works best for you!