FM200 SYSTEM | How does it Work?

Last Updated: August 13, 2023, by

The most common type of FM200 System seen is a total flooding, automatically operated one using zoned smoke heads, installed at a high level and solenoid valves on the bottles to activate and release the gas into an occupied space/un-occupied space controlling the fire by cooling the air, removing one of the three elements needed for a fire to take hold – heat.

FM-200 Systems are not highly complex, and below we will cover the most common type of system components and operation.

Design and Operation Considerations


Any clean agent system should be designed and operated in line with the project specifications and local requirements such as:

  • NFPA 2001 – Standard on Clean Agent Fire Extinguishing Systems,
  • ISO 14520-1 – Gaseous Fire Extinguishing Systems – General Requirements, or
  • BS 15004-1 – Fixed Fire Fighting Systems – Gas Extinguishing Systems
  • UL 2127 – Inert Gas Clean Agent Extinguishing System Units
  • Authority Having Jurisdiction [AHJ]


The system will be designed as automatic detection and discharge ‘total flooding’ system, where the clean agent is released into the protected space in line with the specified and designed concentration and taking into account the NOAEL requirements [No Observable Adverse Effect Level], allowing the suppression and extinguishing of the fire. 

Depending upon the fire type, referring to UL 2127, when using halocarbons [FM200], the minimum design concentration should be between 6.7% and 8.7% at the lowest anticipated room temperature, keeping under the NOAEL for humans [No Observable Adverse Effect Level] requirement of 9%.

The below table details these Halocarbon requirements, including Inert Gaseous Systems for comparison, with discharge times.

HalocarbonsInert Systems
Minimum design concentration at the lowest anticipated room temperature6.7% [Class A Fire], to 8.7% [Class B Fire]34.2% [Class A Fire], to 42% [Class B Fire]
No Observable Adverse Effect Level [NOAEL]9%43%
Human Exposure Limit5 Mins
Discharge Time10 Seconds60 Seconds

System Components and their uses

Control Panel

The control panel provides the overall system monitoring, alarm, activation, and deactivation where all detectors, strobes, beacons, manual call points, interfaces, abort stations, solenoid valves, timers, and trips being connected and controlled by it.

The panel will also provide a history of the system status and events

See our article, 'GASEOUS/FM200 SYSTEM | Functional Testing Template & Download', for a guide on how to functionally test this type of system


Installed as 1No. Zone or Multiple Zones, smoke, and or heat detectors will usually be installed at a high level to monitor the protected space for any signs of fire.

Smoke detectors will be ‘photoelectric’ and fully addressable, using light scattering to measure smoke density.

Heat detectors, using an electronic sensor to monitor the temperature conditions of the space, would usually be rated at 135 degrees F [57 degrees C].

Under regular operation, each detector shall incorporate a red LED that is clearly visible and will constantly ‘flash’ showing normal communication with the system.

The LED will stop ‘flashing’ if there is a fault with communication or remain lit if activated. 

Duct-mounted sensors can also be used.

Solenoid Valves / Electronic Actuators

To ensure that gas is only released from the bottles into the protected space when needed, solenoid valves are installed to activate and open when signaled from the control panel once the fire conditions have been sensed.

They are usually found installed at the outlet of each gas storage bottle.


Sounders are manufactured to meet the correct UL [Underwriters’ Laboratories] requirements. They are connected to the system to warn the occupants in and around the protected space that the system has discovered a fire.

NFPA 72 [A.] notes that the maximum sound pressure level permitted at the minimum hearing distance from a sounder is to be no more than 110 dBA. Depending upon the type of space and background noise, the requirement could be a lot less.

This was changed from the previous sound pressure level of 120 dBA in 2007.

Manufacturers will usually design the sounder so it can use multiple different tones and so the correct sound pressure level can be measured at a minimum of 10 ft [3m] away.

Visual Notification Devices

Visual notification devices are installed, wall/ceiling mounted, in any space where the ambient background noise would exceed 105 dBA, as the sounders would be harder to hear, especially for any hearing impaired.

The strobe intensity should be in accordance with NFPA 72 & UL 1971, and they will provide a visual alert by using a strobe / light warning occupants of any change in status of the space.

Each device will be mounted, ensuring that no portion of the light is blocked or obstructed.

Manual Pull Station / Status Unit

Manual Pull Stations / Status Units are installed remotely [surface/semi flush] from the main extinguishing control panel, usually at each exit to the protected space. They will provide the following information and control:

  • LED Indication, notifying any persons entering the space of the system status 
  • Keyswitch for manual / auto control.
  • Emergency activation of the system, if needed

If the emergency switch is used, the system will not be able to be reset to normal operation.

Hold Button

Surface or semi-flush mounted and using a ‘GREEN’ button; the HOLD can be installed at each entrance and exit to the protected space and are used, where required, to interrupt the gas discharge from the suppression bottles. Usually would be used to allow for investigation or more time for the evacuation of people from the space.

Once the button has been released, the timer for the gas discharge will restart its countdown.

Abort Button

Surface or semi-flush mounted and using a ‘RED’ button; the ABORT can be installed at each entrance and exit to the protected space and are used, where required, to interrupt the gas discharge from the suppression bottles. Usually would be used to allow more time for the evacuation of people from the space.

The suppression system will not be released as long as the button is being pushed; once the button is released, the discharge timer will continue to count down.

Signage, Warnings and Instructions

Signage and warning signs are a requirement of NFPA which notes that they should be provided in the following locations, and they should be fully visible to anyone wanting to enter the space:

  • At entrances to the protected area
  • Inside the protected area
  • Ouside each entrance to the cylinder store room

These types of signs are to be manufactured inline with ANSI Z535.2, Standard for Environmental and Facility Safety Signs.

Other signs that would be installed will be illuminated to provide a clear warning to operatives that the suppression system has been activated.

Primary and Secondary Power Source

To ensure that the system is powered, operating, and ready a dedicated power supply [primary] should be provided and will be either 120v [60Hz] or 240v [50Hz].

A standby power system, local battery, or UPS should also be connected when the primary power supply is not available.

The secondary power should provide enough power to the system to allow its complete operation and activation [monitoring, activation, discharge of gas, lights, sounders, etc.] for a minimum of 5 minutes during and up to 24 hours of the primary power failure

Control System

To allow any suppression system to operate, there will need to be a programmed control system that provides monitoring and correct operation.

The controls are the brain of the complete system, monitoring and commanding all peripheral equipment such as:

  • 1st Stage Smoke / Heat Detectors
  • 2nd Stage Smoke / Heat Detectors 
  • 1st Stage Sounders
  • 2nd Stage Sounders
  • Control of Bottle Solinoid Gas Release Valves
  • Monitoring Pressure/Low Pressure Alarms from Suppression Bottles
  • Abort Switch
  • Hold Off Switch
  • Remote Status Units
  • Signage

Ventilation/Purging System

After the suppression system has been discharged and the fire extinguished, there will usually be a requirement to change the air in the space to ensure that the gas is removed before any persons enter for inspection.

A purge fan and system will be used to complete a total air change of the space.

The system will be activated from outside the protected area, extracting the air from the space and allowing fresh air to enter via a transfer grille or the supply ventilation system.

After a while, the room will be safe to enter.

Sequence of Operation

The following sequence of operation will cover the monitoring and activation of a standard type of gas suppression system:

1Activation of any single detector in Zone.

[1st Stage Detection]
a. System initiates 1st Stage Alarm.

b. Alarm bells & Strobes activate.

c. BMS sends a common alarm.

d. Ventilation and Air Conditioning tripped as per AHJ / specification.

e. Access doors released.

f. Public address activated.
2Activation of any other detector in Zone.

[2nd Stage Detection]
g. Gas discharge timer started [30 seconds]

h. Gas Discharged into the protected area.
3After system dischargeI. Purging system [if installed] available, after discharge.


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