How many fire extinguishers do I need?
There are a number of safety equipment requirements that the Coast Guard inspectors check on board including ventilation ducts, your safety bell, personal floatation devices, and of course, fire extinguishers. There are some slight differences when you look at the regulations of the USCG for commercial and recreational vessels, and the regulations of the American Boat and Yacht Council and the National Fire Protection Association. It will often depend on the service and use of each vessel.
Here is a chart that combines the requirements specified by both the ABYC and NFPA
Click here for chart (printable .pdf file)
The National Fire Protection Association has created the national minimum fire safety standard that exists for all public buildings and places. It is just that, the minimum amount of safety required by law. Their recommendations may be exceeded anytime the application calls for it, but you can never fail to meet the minimum requirements. The same holds true on board. The minimum requirement would be considered mandatory, and based on the layout of the vessel, additional equipment may be logical, if not required.
Again, regard these as recommended minimum standards and place the right amount you need on board to achieve the desired level of assurance with regards to your overall fire safety. Most pleasure yachts will place a small extinguisher in every cabin or stateroom, without regard to the required minimum. If you happen to have a boat you could get lost on, keep in mind you have the potential of having a fire go undetected for a longer amount of time, and it may be severely involved before anyone even notices it. On a smaller vessel you would have greater probability of discovering the fire sooner, or immediately, making your chances of winning that much greater. The locations and amount of equipment necessary are chosen after carefully considering several scenarios that may occur and with little regard to satisfying the inspector at that time. Point being, there is a difference between what you have to have and what you better have. You want to know what the requirements are, but, again, use your head and if theres a hazard on board that even an amateur can spot that should be given special consideration, by all means consider it! This answer is assuming your vessel is used for pleasure and not commercial use!