Recovering R-22 refrigerant from a system with locked compressor
The HVAC technician is required by EPA regulations to recover and recycle all the R-22 that can possibly be recovered.  They should know what to do and should also have the right equipment to do it.
They will use a refrigerant recovery pump that is essentially a vacuum pump that then pumps the recovered R-22 into a tank for proper disposal.
You should not attempt this yourself as it's both dangerous and illegal.