When should you replace the CO2 cylinder of an inflatable PFD?

You should replace the CO2 cylinder of an inflatable PFD when it has been used to inflate the device, if the cylinder shows signs of corrosion or damage, or if the expiration date indicated on the cylinder has passed. Regularly inspect the cylinder and ensure it is properly installed and securely tightened. Additionally, it's advisable to check the PFD's manual for specific manufacturer recommendations on maintenance and replacement intervals.