Hydrocarbons:

This group contains colourless fluids generally in gaseous state and built up of several combinations of hydrogen and carbon. Mostly refrigerants from this category are appropriate for low temperature refrigeration. Isobutene falls in this category & has been appropriate for domestic refrigeration. They are non-poisonous, but are highly explosive and flammable while exposed to air. The boiling point and molecular weight of each gas varies according to the number of carbon and hydrogen atoms. The larger the number of carbon and hydrogen atoms, the heavier is the gas & higher is its boiling point.