Yes, exactly. Those compressors are expensive. Back in my firefighting days, of the 21 or so departments in my county, I think maybe 3 had their own compressors

Yes, exactly. Those compressors are expensive. Back in my firefighting days, of the 21 or so departments in my county, I think maybe 3 had their own compressors. A few more had cascade systems, either at their station, or on a truck. So every couple of weeks or so, the other departments would haul all of their bottles to one of the departments that had a compressor, and refill them all (including the cascade bottles). It really is a bit of a hassle, but it's worth it for an application like firefighting where SCBA are an absolute requirement.