Book excerpt: As the HVACR industry continues to move forward and innovate, the refrigerants that were once so commonplace are now being phased out. Replacing them are more energy efficient, environmentally friendlier refrigerants, known as Low GWP refrigerants. Many of these new refrigerants are classified by ASHRAE as A2L, or slightly flammable. The industry is also seeing expanded use of some hydrocarbon (A3) refrigerants, such as propane and isobutane. Students and technicians will require additional training for the safe handling and transportation of these refrigerants. The Low GWP refrigerant program manual covers: Refrigerant safety Introduction to Low GWP refrigerants Refrigerant properties and characteristics The refrigeration cycle Working with refrigerant blends Proper installation and service guidelines Flammable refrigerant considerations Explanation of the associated codes and standards for A2L refrigerants