Cream chargers are made from steel (the bulb part) that are filled with Nitrous Oxide (N2O). The Nitrous oxide gas that is in cream chargers is used because it dissolves in the fat that is in cream and other foods when under pressure and then expands within the cream or other food once released to a lower pressure. This whips the food product.
Cream chargers do NOT contain Carbon Dioxide (CO2). Carbon dioxide bulbs are not the same as cream chargers. Carbon dioxide bulbs are used to make soda water or carbonated drinks.