Are fire extinguishers fitted in vehicles subject to the same level of service as ones kept inside a building? If yes then how do you manage it as it would be impossible to get all the vehicles together for a service due to business needs.

A couple of my clients run large fleets of vehicles and plant all of which are fitted with fire extinguishers. They both get around the problem by having a change over system. The extinguishers on the vehicles are removed and replaced as part of the routine maintenance/servicing process. The system is managed via their vehicle database. It is a bit expensive but they are always assured that they have in date extinguishers. They both do the same with their vehicle first aid kits and spill control kits.

Yes it is based on a 12 month cycle, but it is rolling so a proportion of the fleet are changed over every month. So you don't need a full set of replacements just around 15% of the total to allow for changeovers, routine failures and usage. The extinguisher company pick up the ones that need checking, maintenance or refilling monthly and leave the same number in their place, the system just rolls on. It works well.