I have been thinking about this for a long time. Are hydrocarbon refrigerants really as dangerous as people claim? I am thinking that there is no way that a small leak will ignite, especially since a unit specifically designed for a flammable gas should have sealed, spark free contacts. And it sustaining a flame is even more unlikely. Think about it- The most common place for a leak is the coils. If the outdoor coil leaks, there is plenty of airflow over the coil to disperse the flammable gas, even from a fairly large leak. I would think that even a leak on the outdoor coil without the system running would be pretty safe because there is likely to be a breeze to disperse the gas. Even if the gas did build up in the unit somehow ignited it with sealed contacts, when the unit started up, I would think that the airflow from the fan would reduce the concentration of the gas to the point of not supporting the flame for more than maybe 1-2 seconds. A possible solution to this problem is to ensure that the outdoor unit is at least a certain distance from the house. An indoor coil leak could be a bit more disastrous though. A small leak with the fan running probably is safe, but if the gas builds up inside the indoor unit with the fan off, a spark from something could ignite it. Another possible risk is if the indoor coil suddenly bursts and causes a very large gas release, no matter how well the gas is dispersed throughout the house, it could reach a high enough concentration to ignite explosively. How likely is it for an indoor coil to suddenly burst? I think that there are ways to safely use a hydrocarbon refrigerant in a home AC system, especially with small units like window AC systems. What do you think?