I have a couple of old extinguishers. A chemical one I have has lost all its pressure. I unscrewed the top and found the powder inside is now a semi-solid. I once looked into getting a Coldfire suppressor but never did. As I understand it, one can buy Coldfire in a 13 oz aerosol can or can by the agent, which you then mix with water, and fill and pressurize the appropriate canister of your choice.
My thought was to empty out the expired extinguisher I have, drill it, install a Schraider valve, and use it to load the Coldfire agent. What's wrong with that plan?