FM-200/Novec System

What makes a clean agent system different from CO2

Both FM-200 and Novec 1230 work primarily by physical heat absorption rather than oxygen displacement, so the design concentration used to extinguish a fire, typically in the range of six to nine percent by volume, remains within limits considered survivable for the short time needed to evacuate. This is the key difference from a CO2 flooding system, which extinguishes by reducing oxygen concentration to a level that also cannot support human life, and therefore demands stricter evacuation and lock-out procedures before discharge. Clean agents are stored as a liquefied gas under pressure and discharge in seconds, filling the protected space uniformly through a network of nozzles.

Main components

Agent storage cylinders

Pressurised cylinders hold the liquefied agent with a nitrogen superpressurisation charge; cylinder pressure is checked periodically as the main indicator of agent retention.

Detection and control panel

Cross-zoned smoke or heat detection triggers an alarm sequence with a time delay before automatic release, giving personnel a window to evacuate or abort the discharge.

Distribution piping and nozzles

Fixed pipework sized by hydraulic calculation delivers agent to nozzles positioned to achieve uniform concentration throughout the protected space within the required discharge time, generally around ten seconds.

Manual release and abort stations

A manual pull station allows immediate discharge, while an abort station lets an occupant hold off automatic release if the space is occupied and the alarm is being investigated.

Space integrity features

Automatic dampers or shutdowns close ventilation openings and stop fans before discharge, since agent concentration cannot be held if the space keeps exchanging air with the outside.

Selection and sizing

Agent quantity is calculated from the protected space's net volume, the required design concentration for the agent and the fire risk class present, with a margin for the space's enclosure integrity (leakage through cable and pipe penetrations). Novec 1230 requires a larger stored liquid volume than FM-200 for the same protected volume, which affects cylinder room space and weight, a real consideration on smaller vessels.

Regulations and class

SOLAS Chapter II-2 and the IMO Fire Safety Systems (FSS) Code govern fixed gas fire-extinguishing systems, including agent quantity, discharge time and alarm sequencing, with the specific chapter applied depending on the protected space and its size. Flag and class requirements call for periodic weighing or pressure checks of cylinders and functional testing of the detection and release sequence, since these agents are also subject to environmental phase-out schedules that affect long-term parts and refill availability.

Typical faults

• Low cylinder pressure or agent loss - a slow valve or fitting leak reduces the stored quantity below the calculated design amount, so a real discharge would not reach extinguishing concentration.
• Space integrity loss - new cable runs or ventilation modifications after the original design create leak paths that let agent concentration fall below the effective level before the fire is out.
• Detection system false alarms or failures - dust or oil mist fouling smoke detectors either triggers nuisance discharges or, if desensitised in response, delays real detection.
• Damper or fan interlock failure - if ventilation does not shut down automatically on discharge, agent concentration is diluted continuously and never reaches design level.
• Neglected abort station testing - an abort function that has not been tested may not work when actually needed, forcing an unnecessary full discharge during routine work in the space.

What to look for in a supplier

• System design calculations matched to the actual as-built space volume and enclosure, not a generic per-cubic-metre estimate.
• Cylinder refill and testing service available in the ship's trading area, given that agent and cylinder testing has specific handling requirements.
• Clear guidance on the agent's long-term regulatory status, since environmental rules on fluorinated gases continue to evolve and affect future availability.
• Documented compatibility with the ship's existing detection and alarm panel if only part of the system is being renewed.

Room integrity, not agent quantity on paper, decides whether a clean agent system actually extinguishes a fire - treat every new penetration through a protected space's boundary as a system modification that needs sign-off.