I love how the law works...
R134a in your car is classified as "Refrigerant" = bad, no vent!
in your duster gas classified as a "Propellant" so no problem!
In some plastics manufacturing is a "blowing agent" also, no problem vent away!
r134a is also has medical applications such as, (I would imagine) if anyone uses an inhaler, theres probably some R134a in there.
r134a is a relatively low pressure gas, even lower than propane at any given temperature.
r410a, now theres a nice gas. It is a blended refrigerant (r125 and something else I cant remember) but it is near azeotropic which means that it has low glide/fractionation. Why is that important in airsoft? Because the higher pressure gas will sit at the top of the mag and get used first, leaving the lower pressure gas in the last half of the mag; if there is a signifgant pressure difference between the two gasses you would notice a loss of performance shooting the second half of the mag.
Anyway, long story short, I'm running it in GHK AKM green gas mags without a problem. Seals are holding fine, and I'm not really worried about the mag exploding even though r410a is about twice the pressure of Propane at any given temperature (so on a hot day around 250 psi) as I hear some ppl are actually running CO2 in the GHK green gas mags with no problem and thats at least 10 times the pressure. Because the boiling point is so low, the mags have nice recovery time, and really kick. Can shoot well over 500fps, but I've got it trimmed down to just under 380fps with FG airsofts nozzle. In the field, all of these new HFC refrigerants use synthetic oil (POE) and rubber is still commonly used, so I think silicone will be just fine on the seals.
I would really only consider duster gas if you were looking to downgrade your fps on a hot shooting pistol/rifle and couldn't get an npas for it or something.