We do not know what you mean by "PFD", please do not use abbreviations. But the answer would be when the instructions for the "PFD" say it needs to be replaced.
Every time the PFD is worn
discard because they are unusable
When selecting a PFD, the most important consideration should be size.
Every time the PFD is worn
When selecting a PFD, the most important consideration should be size.
Every time the PFD is worn
Every time the PFD is worn
Every time the PFD is worn
Every time the PFD is worn
Securely fasten your PFD, and wait for help.
When should you discard a PFD?