Explain why a smaller coded yacht might rely primarily on portable extinguishers and a simple fixed system in the machinery space, while a larger coded yacht has a more extensive fixed fire-fighting installation, and what determines the difference.

A. FIXED FIRE-FIGHTING SYSTEM SCALING UNDER THE CODE: The extent of fixed fire-extinguishing system requirements (e.g. CO2 or other fixed gas systems in machinery spaces, fixed systems in paint lockers/other high-risk spaces) scales with vessel size and machinery space risk, in the same proportionate way structural fire protection does. A smaller yacht with a smaller, lower-risk machinery space may meet the Code's requirements with a more limited fixed system plus portable extinguishers, while a larger yacht — particularly one at or above the 500GT structural fire protection threshold — will be required to have a more extensive fixed system matched to the larger machinery space volume and the higher passenger-ship-derived standard that applies above that threshold. DETERMINING FACTORS: (1) Machinery space volume and the type of equipment/fuel risk present; (2) The vessel's GT band (as with structural fire protection, ≥500GT triggers the more demanding passenger-ship-derived standard); (3) Specific high-risk spaces (paint lockers, fuel pump rooms) which carry their own fixed-system requirements regardless of overall vessel size. CREW IMPLICATION: an officer should never assume a fixed system's headcount-clearance procedure, activation sequence or pre-discharge alarm timing is identical between yachts of different sizes — always confirm the specific vessel's system and procedure rather than relying on experience from a previous, differently-sized yacht.

B. Fixed fire-extinguishing system requirements are identical for all coded yachts regardless of size, machinery space volume or GT band.

C. Only yachts over 3,000GT are required to have any fixed fire-extinguishing system; smaller coded yachts rely exclusively on portable extinguishers under the Code.

D. The type of fixed fire-extinguishing system used is solely the yacht builder's commercial choice with no Code requirement governing machinery space protection.

A. STRUCTURAL FIRE PROTECTION SCALING UNDER THE CODE: For yachts at or above 500GT, structural fire protection requirements are derived from SOLAS passenger ship rules applicable to ships carrying fewer than 36 passengers — meaning more extensive fire-resisting bulkhead/deck divisions, stricter fire integrity ratings, and more comprehensive main vertical/horizontal zone subdivision. Below 500GT, the Code applies a proportionately reduced standard reflecting the smaller scale of the vessel and lower absolute fire risk exposure, while still requiring proper compartmentation and insulation standards (e.g. A-class/B-class divisions appropriate to the space). PRACTICAL EFFECT: a 600GT yacht crossing the 500GT line must meet the more demanding passenger-ship-derived standard in full, while a 480GT yacht just under the line is not required to meet that same level — this is precisely why GT, not just length or layout similarity, drives a real difference in required fire protection between two superficially similar vessels. CREW IMPLICATION: an officer transferring between a sub-500GT and a 500GT+ yacht should not assume the same fire safety standard or zone layout applies — review the specific vessel's fire control plan and CCC rather than relying on experience from a similarly-sized yacht under a different tonnage band.

B. Tonnage has no bearing on structural fire protection standards under the Code; all coded yachts above 24m regardless of GT must meet an identical fixed standard.

C. Fire protection standards are set entirely by the yacht's classification society on a vessel-by-vessel basis with no reference to GT thresholds in the Code itself.

D. The 500GT threshold only affects manning requirements, not fire protection — fire safety standards are governed solely by passenger numbers under the Code.

A. A-CLASS / B-CLASS FIRE INSULATION STANDARDS — MACHINERY SPACES: Under the Code's structural fire protection requirements, decks and boundaries enclosing machinery spaces must be insulated to reach a defined fire-resistance standard for a defined period: A-30 means the division must remain effective as a fire/smoke barrier and limit temperature rise on the unexposed side for at least 30 minutes under standard fire test conditions, required for vessels in UNRESTRICTED SERVICE (i.e. capable of extended ocean passages, away from immediate rescue/shore-based fire support). B-15 is a lower fire-resistance class (15 minutes) permitted for vessels operating only in SHORT RANGE NAVIGATION (a more limited area, generally closer to shore/assistance), reflecting the reduced risk exposure and faster potential access to external assistance. WHY THE DIFFERENCE EXISTS: the Code's structural fire protection requirements are calibrated to the realistic time a crew may need to contain and fight a fire before either bringing it under control or reaching a point where external assistance/evacuation becomes practical — a vessel restricted to coastal/short-range operation can rely on a shorter self-sufficiency window than one on an unrestricted ocean passage far from any assistance. PRACTICAL POINT FOR CREW: the vessel's actual service notation (unrestricted vs short range) is not just an operational limitation — it is tied directly to the fire insulation standard the vessel was built and surveyed to, so operating outside the certificated service notation can mean operating with fire protection inadequate for that profile.

B. A-30 and B-15 refer to the colour-coding of fire extinguishers required in machinery spaces, not to structural insulation standards.

C. A-30 applies to short range navigation vessels and B-15 applies to unrestricted service vessels — the reverse of the higher standard being for greater self-sufficiency.

D. These classifications are obsolete terminology from LY1 and no longer appear in any current edition of the Code.