bjr, I service about 1200 fire extinguishers a year, refilling at least 300. The biggest problem that you will encounter is pressurizing to 195 psi. We use bottled nitrogen via a regulator. Air works if it's dry enough. You can buy the powder from any of the manufacturers but unless you're filling quite a few it won't be economical. We buy 2 tons per delivery in 5 gallon/45lb buckets. The yellow pages should provide a service center near you if you have just a few extinguishers to fill. If there's nothing in the yellow pages look at the extinguisher tags in a dept store (the ones on the wall for emergencies - not the ones for sale), many stores rent extinguishers with a service contract & will have a vendor label. If you fill your own you need to completely disassemble & clean the valve, which is easy to do. If not completely clean the pressure will bleed off. Send me a PM if you want more detailed info. Mike