the volume in a pipe is a lot less than what you'd find in a tank, especially considering the pressure in said pipes is usually one tenth of a psi (.6 kPa)
In the US it's typically more like 0.25psi, I don't know about elsewhere.
But it's connected to what you might consider a tank of nearly infinite volume. It's flow rate limited, but it's fast enough to get an entire house to explosion concentration in much less than a day. Perhaps only an hour.
Point is that we humans manage to figure out how to harness things that might be dangerous when they're useful. And hydrocarbon refrigerants can be very useful so we might figure out how to deal with the relatively small danger they pose.
A fuel-air explosion will not be contained by a reasonable amount of concrete or masonry. The real safety lesson is to control sources of ignition and prevent the buildup of released gases.
Notably, Propane has almost identical refrigeration characteristics to R-22, so it was an easy drop-in replacement for systems designed for R-22 when that was banned.