When should I replace the Co2 in an inflatable pfd?

You should replace the CO2 cartridge in an inflatable personal flotation device (PFD) after it has been activated or if you notice any signs of corrosion or damage. Additionally, it's advisable to check the cartridge regularly, especially before any water activities, to ensure it is properly sealed and functioning. Always follow the manufacturer's guidelines for replacement and maintenance to ensure the PFD remains safe and effective.