What Automotive Fire Extinguishers Can Clarify
A properly rated, securely mounted, maintained extinguisher may help control a very small incipient fire when the user is trained, escape is clear, and emergency services have been called.
It is most useful when fitment, installation, safety, and maintenance all support storing a correctly rated portable extinguisher in a secure accessible vehicle mount for limited use only on a small incipient fire when escape remains clear and conditions are safe.
Where the Shortcut Breaks Down
It cannot make fighting a vehicle fire generally safe or replace immediate evacuation and emergency response, and it cannot compensate for opening a hot hood or trunk, battery thermal runaway, fuel involvement, smoke exposure, an unclear escape path, wrong rating, low pressure, corrosion, expired service, insecure mounting, or delayed calls to emergency services.
A better decision compares the system around the part, not only the headline feature or product photo.