what's the song that's goes, &I'm the king of the ring ring..&?
Depress the release valve on the extinguisher in a well-ventilated area outdoors that is away from where children or animals. Make sure that the extinguisher is completely depressurized. Place the extinguisher unit in the trash if there are no restrictions against doing so. If you are not allowed to throw the extinguisher away, contact an extinguisher service that offers dry chemical extinguisher disposal and arrange for the extinguisher to be picked up or dropped off.
Question, Is it all the door locks that don't work or just one door? You really need to answer this question before anybody can take an educated guess.