In addition to the flame hazard of the oil, all fluorinated refrigerants create nasty, toxic fumes when exposed to flames even if they don’t burn. If you have ever gotten a strong snort of this stuff you know it is an experience to be avoided.
One more reason to be cautious now is the presence of so many refrigerant blends with small quantities of hydrocarbons in them. Although the quantity of hydrocarbons is small, the hydrocarbons can concentrate in the compressor oil when charged into a system with mineral oil. Even after recovery, there can still be volatile hydrocarbons in the compressor oil. You heat it to de-braze the compressor, and a flammable gas comes out when you pull the pipe loose. I have heard one story where the technician was de-brazing a compressor and was engulfed in a ball of flames for a short period of time after pulling the line out of the compressor. It was a brief flash fire that burned off his eyebrows and gave him a sunburn, nothing too serious – but definitely scary. The refrigerant was an R22 replacement rated A1/A1. Also, consider that with so many replacement refrigerants you really don’t know exactly what is in the system. Although the highly flammable R22 replacement refrigerants are illegal, they are widely available on the internet and they are sold to anyone with a credit card. Just on the off chance that the system you are working on was topped off with propane, you should avoid de-brazing. Make sure and purge the system with nitrogen before brazing the new compressor in. Not only will you avoid oxides inside the lines, you might also avoid fires in the area you are working in. I believe refrigerants with some degree of flammability will become more common. To be safe, we need to start treating all systems as if the refrigerant could burn. So the next time you have to remove a refrigeration component – CUT IT OUT!