Do you know what type of refrigerant your air conditioning system uses? The answer is probably no. Most people's concerns around ACs revolve around whether they’re properly cooling, dehumidifying and filtering the air in a home, and at what cost. But it's important to know that last year, the U.S. Environmental Protection Agency (or EPA) changed the rules regarding the types of chemicals that can be used in heating, ventilation and air conditioning (HVAC) systems.