Can I safely cut a copper compressor pipe with r600a gas?
Venting a flammable gas may be safe as long as there are no sources of ignition in the area and the gas has time to dissipate. Kind of like having a propane or LP gas cylinder filled once the cylinder is full they vent the gas between the pipe and fill valve. Outside away from ignition sources this is considered safe so I would expect the same to be true with the isobutane.