https://blog.gongquiz.com/2021/05/03/%ec%b2%ad%ec%a0%95%ec%86%8c%ed%99%94%ec%95%bd%ec%a0%9c-%ec%a4%91-hcfc-blend-a%eb%a5%bc-%ea%b5%ac%ec%84%b1%ed%95%98%eb%8a%94-%ec%84%b1%eb%b6%84%ec%9d%b4-%ec%95%84%eb%8b%8c-%ea%b2%83%ec%9d%80/