Can I service my own extinguishers?

No, definitely not, and we would certainly not advise this in any circumstances; no credible company would promote this in any form. There are many parts to a fire extinguisher other than the vessel itself, such as the pressure gauge, handles, hose, nozzle, down pipe etc. etc. If, for example, a pressure gauge was faulty only a trained engineer could tell this with the equipment they carry. If ever faced with a fire, you need some assurances your extinguishers will work. The fire safety order exists for this purpose. Article 3 explains the meaning of a “responsible person” which means the owner or ultimate responsible person for a business, and their obligations which are “unconditional”.