What are regulation for number of Portable Fire Extinguishers on ships ?

As per SOLAS, chapter II-2,

The number of portable fire extinguishers required by regulation 6.7 is the number required to satisfy classification society rules and in no case less than 5 for ships of 1000 gross tonnage and Upwards.

Points to pounder for fire extinguisher:

1. For fire extinguishers of the same type, capable of being recharged on board, the spare charges should be provided as follows: 100% for the first 10 extinguishers and 50% for the remaining extinguishers but not more than 60 (fractions to be rounded off to next whole number).
2. For extinguishers which cannot be recharged by the crew, additional portable fire extinguishers of the same quantity, type, capacity and number as determined in paragraph a above should be provided in lieu of spare charges.
3. Instructions for recharging the extinguishers should be carried on board. Periodic refilling of the cylinders should be in accordance with the manufacturer’s recommendations. Lacking same, refill is required when the extinguishing media starts to lose effectiveness. Partially emptied extinguishers should also be  recharged. Only refills approved for the fire extinguisher in question may be used for recharging.

Note :

• If the loss of gas from a carbon dioxide extinguisher or propellant bottle of any other type of extinguisher exceeds by 10% of the original charge as stamped on the extinguisher or bottle, then extinguisher or bottle should be recharged. Any extinguisher or bottle which has excessive external corrosion should be replaced.
• In surveying the safety equipment on a vessel classification societies should verify that:
  • The manufacturer’s instructions for recharging extinguishers are on board;
  • The extinguishers have been inspected and maintained in accordance with the manufacturer’s instructions and the foregoing requirements;
  • Records of inspections, maintenance and pressure tests are maintained.