Cooling machines, like fridges and air conditioners, use chemical gases to work. The old gases, CFCs and HCFCs (chlorofluorocarbons and hydrochlorofluorocarbons), damaged the ozone layer and have been phased out, thanks to the 1987 Montreal Protocol.The old gases were replaced by HFCs (hydrofluorocarbons). HFCs do not damage the ozone layer, but they are greenhouse gases 1000 to 9000 stronger than carbon dioxide.So in October 2016, 170 countries met in Kigali, Rwanda, to make a deal for HFCs.High-income countries will start phasing them out in 2019.Some low-income countries will start phasing them out in 2024.Other countries will start phasing them out in 2028.There are safer natural refrigerants available, like propane and ammonia.Scientists think the Kigali accord will reduce global warming by nearly one degree Fahrenheit.The most dangerous time for these gases is when the fridges and air conditioners are finished. The gases have to be carefully removed and stored. They can be transformed into other less dangerous chemicals that do not cause global warming.