When such test data is not available, the supplier will base the classification on test data collected on the individual ingredients that make up the product. A Cylinders store compressed gases under pressure. Gases which are also flammable, toxic or have other hazardous properties, will also be found in other classes. In addition to the compressed gas symbol, such gases also carry the symbol appropriate to the class. Oxygen which is used in both health care and welding, and ammonia which is used in large refrigeration systems, are typical compressed gases.
Acetylene is another compressed gas which is also widely used in welding.
Dalhousie research laboratories also use a wide range of gases. Nitrogen, helium are among the most common of these laboratory compressed gases. There are 6 subdivisions to the flammable and combustible materials class. Containers of chemicals included in each of the 6 flammable and combustible materials subdivisions all carry the familiar stylized flame symbol. All gases such as hydrogen, methane and propane, which can form ignitable mixtures in air, are classed as flammable gases.