R22 is a gas used in Air-conditioning and other appliance which was banned in 2014 from all new AC equipment, due to its detrimental effects on the Ozone layer. From 2015, it is illegal to maintain existing AC equipment which used R22 gas. What this means for tenants is when buying into a 5 year lease (which is the industry standard in this market) you must take into consideration who will be responsible for replacing the AC units if they break.