Refrigerants are what make air conditioning possible. Contained within the coils of an air conditioner, these liquid agents cool and dehumidify indoor air. For years, the most common refrigerant used in air-conditioning systems was R-22. In response to growing environmental concerns, production of systems using R-22 refrigerant is being phased out. Lennox has led the way in the manufacture of cooling systems that use chlorine-free R-410A refrigerant. Because R-410A contains no chlorine, it is considered ozone-friendly. Additional benefits Lennox' highest efficiency cooling systems are designed to use R-410A refrigerant, therefore providing an economic benefit in addition to the environmental benefit. Lennox' R-410A systems are also known for improved reliability, quieter operation, improved dehumidification and enhanced heat pump performance.