Carbon Dioxide:

Carbon dioxide (molecular weight 44) is a non-poisonous and non-toxic refrigerant. Also, this is not only non-flammable but and is an outstanding extinguishing agent as well. Its other advantages are that this is chemically constant, immiscible along the lubricating oil and does not influence the metal utilized in the system. It contains a low specific volume and this needs volume displacement per ton of refrigeration. But, its critical pressure is too high. Also, its critical temperature is just 31 ⁰C that makes it inappropriate for use in countries along a hot climate. This is an excellent refrigerant for low temperature refrigeration.