Fire Suppression Systems

APPROVAL GUIDANCE & INFORMATION:  46 CFR 162.027 specifies compliance of nozzles with ASTM Standard F1546 “Standard Specification for Fire Hose Nozzles”.  Due to the extensive testing requirements of ASTM F1546, the Coast Guard will approve brass or bronze nozzles that meet the performance criteria of NFPA 1964.  The Coast Guard does not test materials or systems for approval but rather specifies the required test methods and minimum performance criteria for approval.  Product testing must be performed by a Coast Guard Accepted Independent Laboratory. 

SUBMITTAL PACKAGE:  Please submit the following information in the Submittal Package:

• A cover letter requesting Coast Guard Type Approval of the equipment.
• A test report from the Accepted Independent Laboratory showing compliance of the product or equipment with either ASTM F1546 or NFPA 1964 for brass nozzles.
• Evidence that an acceptable follow-up factory inspection program is in place in each factory location.  This could be demonstrated by providing an original copy of the contract for a follow-up program between the manufacturer and the Accepted Independent Laboratory.  The follow-up program must show that no unauthorized changes can be made to the equipment without proper review and approval by the Accepted Independent Laboratory.
• Required drawings/plans of the equipment.  At a minimum, this should include an exterior drawing, an assemble drawing and a list of components as well as a bill of material.

APPROVAL GUIDANCE & INFORMATION:  U.S. Coast Guard regulations require the installation of U.S. Coast Guard approved fixed gaseous extinguishing systems on certain U.S. registered inspected vessels and permit the substitution of an approved system for one of the required approved portable fire extinguisher on pleasure craft.

In order to obtain a certificate of approval (i.e. type approval), compliance with the following criteria is required.  These criteria determine the equivalency of new clean agent systems to the carbon dioxide systems currently specified in the various vessel regulations, and to the halon systems previously approved as equivalent to carbon dioxide systems.  This updates and supplements the test program outlined in our Notice of Proposed Rulemaking published in the Federal Register on Wednesday, January 9, 1991, pages 829 through 836, to enable inclusion of clean agent replacements for halons.

1)    Approvals are issued only for complete systems made up of specific components and utilizing specific extinguishing agents.  Approval is not issued for individual system components, such as individual hardware or extinguishing agents.  The Coast Guard does not test materials or systems for approval but rather specifies the required test methods and minimum performance criteria for approval.  Product testing must be performed by a Coast Guard Accepted Independent Laboratory.

2)    The extinguishing agent must be acceptable to the U.S. Environmental Protection Agency (EPA) under the Significant New Alternatives Policy (SNAP list) without restrictions that limit its use in marine applications.

3)    The agent must be recognized as a fire extinguishing medium by NFPA 2001 on Clean Agent Fire Extinguishing Systems.

4)    Systems must be listed and labeled for marine use by an independent testing laboratory accepted by the Coast Guard under 46 CFR 159.010.  Laboratories currently can be found online at CGMIX Accepted Laboratories List.  All tests must be conducted under the control of the laboratory.  To be acceptable, the laboratory must apply and be accepted in accordance with 46CFR 159.010 prior to conducting any tests.  A laboratory must demonstrate independence and technical expertise in the evaluation of the fire suppression systems in accordance with the latter regulation.

5)    Systems must be intended for installation in spaces that are normally unoccupied, and that personnel can leave within 10 seconds after the system is actuated.

6)    Systems are approved based on fire tests in simulated compartments of pre-determined size, and are not designed individually for each engine compartment.

7)    The primary system actuator must be automatic if the agent cylinder is installed in the protected space.

8)    Systems must have discharge indicators for installation at each helmsman’s position.

9)    System components must meet UL 2166 “Standard for Halocarbon clean agent Extinguishing System Units”, March 22, 2001 revision (46 CFR 162.161-2).   Subsequent revisions of UL 2166 may be used for the corresponding components and fire tests as required by paragraph numbers 19 and 20 of this section.

10)   System must be intended for the protection against Class B hazards (flammable liquids) in machinery and bilge spaces, and Class C hazards (non-shock hazard when applied to energized electrical equipment).

11)   Systems intended for installation in small passenger vessel (46 CFR Subchapters T and K) must have manual (mechanical) back-up actuators, audible alarms, and automatic engine and ventilation shutdown upon system discharge.  The engine shutdown feature must have a mechanism to quickly restart the engine(s).

12)   Systems using fusible elements for actuation are limited to installation in spaces not exceeding 2000 cubic feet.  Systems for larger unoccupied spaces or any spaces intended for human occupancy must be specifically designed for each space protected, i. e. engineered, and must provide personnel safeguards such as limits on the agent concentration, discharge delays, and pre-discharge alarms.

13)   Systems for fishing industry vessels are limited to spaces not exceeding a volume of 1200 cubic feet.

14)   The volume of the compartment protected must be the gross volume: the length times the width times the depth of the compartment.  The volume of installed equipment such as engine blocks and fuel tanks may not be deducted, unless the boat manufacturer provides a factory installed placard that states the volume of the installed tanks and engine blocks.

15)   Systems must be self-contained, i.e. not require an external source of power such as the boat’s electrical system for activation.

16)   Systems must be intended for installation in engine compartments where natural ventilation does not exceed one air change per minute.  If mechanical ventilation is provided or if the natural ventilation is expected to be greater, a system tested under the higher air flow conditions must be installed.

17)   Systems containing a charge of nitrogen in addition to the extinguishing agent must have a listed pressure gage.  This gage is not a substitute for the required discharge indicator.

18)   Systems intended for installation in volumes of 1000 cubic feet and larger must have a manual back-up actuator.

19)   The system components must be tested by the independent lab as follows:

20)   Fire tests must be conducted in accordance with UL 2166.  For systems without piping, the fire tests of section 36 and SA8 of UL 2166 must be conducted.  The test must be repeated at the system manufacturer’s design concentration and under conditions of one air change per minute for the test enclosure.

21)   For the latter the test compartment must be ventilated at one air change per minute.  Systems not incorporating an automatic engine shutdown feature must have placards for attaching to each helmsman’s position stating that the engine(s), generator, and any powered ventilation must be manually shutdown upon system activation.

22)   Each system must have an owner’s instruction manual containing installation and maintenance instructions.  Systems for pleasure craft are generally intended to be installed by the boat owner.  Systems for inspected vessels are more complex since they require engine shutdowns, and are to be installed by system distributors or marine electricians.  The owners manual must be specific to marine applications and must include the following:

SUBMITTAL PACKAGE:  Please submit the following information in the Submittal Package:

• A cover letter requesting Coast Guard Type Approval of the equipment.
• A test report from the independent laboratory showing compliance of the product or equipment with UL2166.
• Evidence that an acceptable follow-up factory inspection program is in place in each factory location.  This could be demonstrated by providing an original copy of the contract for a follow-up program between the manufacturer and the Accepted Independent Laboratory.  The follow-up program must show that no unauthorized changes can be made to the equipment without proper review and approval by the Accepted Independent Laboratory.
• An installation and maintenance manual as per paragraph number 22 of this section.

APPROVAL GUIDANCE & INFORMATION:  Subchapter D of Title 46 of the Code of Federal Regulations (CFR) requires the installation of fixed low expansion foam fire extinguishing systems on decks of tankers for the protection of all cargo tanks.  These systems are intended to provide protection against flammable liquid fires in the cargo area.  An explanation of the basic characteristics of marine foam systems is contained in USCG Navigation and Vessel Inspection Circular (NVIC) No. 6-72.  These systems must be designed to:

1.      Extinguish the fire:  Each foam formulation (type, percentage, etc.) must successfully extinguish a series of test fires using fuels representative of the type of cargoes carried on the vessels for which the systems are intended, as for example, gasoline as a test fuel for hydrocarbon cargoes.  Tests will include foam generated with fresh and synthetic sea water.

2.      Prevent re-ignition of the fuel for a period of time:  Each foam must demonstrate its ability to prevent ignition sources above the foam blanket from igniting the fuel below the foam blanket.  In addition, the foams must prevent fire of small areas of exposed to fuel from increasing in size.

3.      Resist foam breakdown and provide a seal against hot metal:  As part of the above, each foam must demonstrate its ability to form an effective blanket, and to resist foam breakdown due to contact with hot metal.

Approval is granted only for complete systems.  Foam concentrates and individual components such as nozzles and monitors are not type approved individually; however, combinations of such components complying with UL 162 may be used to meet requirements for SOLAS "portable foam applicators" (see: Marine Inspection Notice).

Fire tests of foam concentrate

Foam concentrates are subjected to marine fire extinguishment and burn back tests in accordance with the National Fire Protection Association Standard No. 11, Annex F.  This test method was derived from Fed. Spec. O-F-555C, and is designed to evaluate the fire extinguishing capability of the foam concentrate when applied with a standard nozzle in a manner representative of ship-board applications.

Foam quality tests using the standard nozzle are conducted during this test series, and the foam quality obtained during this test series is compared to the foam quality obtained from the systems manufacturer’s hand line nozzles and turret monitors.

The fire tests must be conducted either at UL’s indoor facilities, or other facilities acceptable to the USCG.

A safety factor of 8/3 times the foam applications rate during the fire test will be applied to establish the minimum design foam application rate.

System component tests in accordance with UL 162

System components must demonstrate satisfactory performance when tested for compliance with Underwriters Laboratories, Inc. (UL) Standard No. 162.  These tests include proportioning, foam quality, hydrostatic strength, leakage, friction loss, and exposure of components to the liquid concentrate.  The foam quality must compare to the foam quality obtained during the above fire test within the tolerances specified by UL 162.

Polar solvents

Polar solvent foam systems are water miscible products such as alcohols and ketones which attack regular fire fighting foams.  Special polar solvent or alcohol resistant foams have therefore been developed where the foam application rate varies with the particular polar solvent cargo.  Polar solvent cargoes may be protected with a uniform high SOLAS polar solvent foam application rate, or with specific lower application rates for specific polar solvent groups based on fire tests of representative cargoes.  NVIC 11-82 provides details.

Foam concentrates intended for the protection of polar solvent cargoes must be tested (in addition to being effective on hydrocarbon fuels) using several selected polar solvent fuels which are representative of specific classes of fuels (such as esters, ketones, acids, etc.).  These tests are conducted in accordance with the relevant sections of UL 162, and will establish the foam application rate necessary for each category of polar solvents.

UL Listing

The foam concentrate must be UL listed.

UL Listing of marine foam systems as a whole is preferred but has not been enforced.  However, foam system components submitted are usually already UL Listed for industrial applications.  UL Listing reports for various foam system components are therefore given consideration in lieu of new tests.

Any non-collapsible (hard rubber) hose must either be UL Listed or be of comparable construction.

Component tests in addition to UL 162

Foam discharge range tests using monitor turrets must be conducted to determine the effective range of foam discharge.  The design range of the monitors as reflected in the system Manual is limited to 75% of the tested still air range.

The compatibility of any metallic or nonmetallic tank material with the various foam concentrates must be established.

ASME pressure tanks must meet the criteria of Subchapter F of Title 46 of the CFR.

Piping sections carrying AFFF concentrate (not foam solutions) must be made of stainless steel.

The Coast Guard does not test materials or systems for approval but rather specifies the required test methods and minimum performance criteria for approval.  Product testing must be performed by a Coast Guard Accepted Independent Laboratory.

SUBMITTAL PACKAGE:  Please submit the follow information in the Submittal Package:

• A cover letter requesting Coast Guard Type Approval of the equipment.
• A test report from the Accepted Independent Laboratory showing compliance of the product or equipment with the above requirements.
• Evidence that an acceptable follow-up factory inspection program is in place in each factory location.  This could be demonstrated by providing an original copy of the contract for a follow-up program between the manufacturer and the independent laboratory.  The follow-up program must show that no unauthorized changes can be made to the equipment without proper review and approval by the Accepted Independent Laboratory.
• Draft marine design, operation, installation, and maintenance manual.  The draft Manual should include the following information:

1. Conspicuous warning signs to be posted by the entrances to carbon dioxide cylinder rooms, any spaces protected by carbon dioxide systems, and any adjacent spaces where carbon dioxide could migrate;
2. Evacuation of all normally occupies spaces before the extinguishing agent is discharged;
3. Pre-discharge warning sirens in the protested space that sound for a sufficient period of time to allow the crew to evacuate the space before the discharge begins; and
4. System releasing stations designed to require the operation of two separate and distinct controls before system discharge is initiated, to prevent a single action from accidentally releasing the system.

• A cover letter requesting Coast Guard Type Approval of the equipment.
• A test report from the Accepted Independent Laboratory showing compliance of the product or equipment with the applicable UL requirements and Coast Guard vessel regulations.  Please refer to Subchapter D, H, I, I-A, K, R, and U for the details of the system types.
• Evidence that an acceptable follow-up factory inspection program is in place in each factory location.  This could be demonstrated by providing an original copy of the contract for a follow-up program between the manufacturer and the Accepted Independent Laboratory.  The follow-up program must show that no unauthorized changes can be made to the equipment without proper review and approval by the Accepted Independent Laboratory.
• Draft marine design, operation, installation, and maintenance manual.  The draft manual should include the following information:
  1. Description of system design, including system schematic.
  2. A complete list of components.
  3. Drawings of major system components, such as nozzles, selector valves, agent storage cylinders, etc.
  4. Sample computer program input sheets.
  5. Sample calculations and drawings for typical system installations in accordance with the applicable vessel regulations (such as 46 CFR 95.15 for cargo vessels) which will enable USCG personnel to verify calculations for each system installed on a specific vessel.
  6. Samples of warning labels on the hazards of carbon dioxide.

APPROVAL GUIDANCE: In 2012, the Coast Guard regulations were amended to accept engineered clean agent extinguishing systems as equivalent to fixed carbon dioxide systems for all applications except for the protection of cargo holds. Detailed type approval criteria for both halocarbon and inert gas clean agents may be found in 46 CFR 162.161, while design installation and testing requirements are listed in 46 CFR 95.16. General type approval criteria are summarized below:

1.      Approvals are issued only for complete systems utilizing specific extinguishing agents.  Approval is not issued for individual system components, hardware, or extinguishing agents.

2.      The agent must be acceptable to the U.S. Environmental Protection Agency (EPA) for use in occupied spaces under the Significant New Alternatives Policy (SNAP list).

3.      The agent must be recognized as a fire extinguishing medium by NFPA Standard 2001, Standard on Clean Agent Fire Extinguishing Systems.

4.      The system must successfully pass the fire tests in IMO MSC/Circ. 848, Revised Guidelines for the approval of equivalent fixed gas fire-extinguishing systems, as referred to in SOLAS 74, for machinery spaces and cargo pump-rooms, as further amended by MSC.1/Circ. 1267.

5.      The system must be listed and labeled for marine use by a Coast Guard accepted independent testing laboratory.

6.      The system must have an associated marine design, installation, operation, and maintenance manual. The manual must be specific to marine applications and must include the following:
 

• Limitations on nozzle placement and spacing determined from the type approval tests.
• Description of system design, including system schematic.
• A complete list of components.
• Drawings of major system components, such as nozzles, selector valves, agent storage cylinders or tanks, etc.
• Sample computer program input sheets.
• Sample calculations and drawings for typical system installations in accordance with the applicable vessel regulations (such as 46 CFR 95.15 for cargo vessels) which will enable USCG personnel to verify calculations.

APPROVAL GUIDANCE: In 2012, the Coast Guard regulations were amended to accept engineered clean agent extinguishing systems as equivalent to fixed carbon dioxide systems for all applications except for the protection of cargo holds. Detailed type approval criteria for both halocarbon and inert gas clean agents may be found in 46 CFR 162.161, while design installation and testing requirements are listed in 46 CFR 95.16. General type approval criteria are summarized below:

1.      Approvals are issued only for complete systems utilizing specific extinguishing agents.  Approval is not issued for individual system components, hardware, or extinguishing agents.

2.      The agent must be acceptable to the U.S. Environmental Protection Agency (EPA) for use in occupied spaces under the Significant New Alternatives Policy (SNAP list).

3.      The agent must be recognized as a fire extinguishing medium by NFPA Standard 2001, Standard on Clean Agent Fire Extinguishing Systems.

4.      The system must successfully pass the fire tests in IMO MSC/Circ. 848, Revised Guidelines for the approval of equivalent fixed gas fire-extinguishing systems, as referred to in SOLAS 74, for machinery spaces and cargo pump-rooms, as further amended by MSC.1/Circ. 1267.

5.      The system must be listed and labeled for marine use by a Coast Guard accepted independent testing laboratory.

6.      The system must have an associated marine design, installation, operation, and maintenance manual. The manual must be specific to marine applications and must include the following:
 

• Limitations on nozzle placement and spacing determined from the type approval tests.
• Description of system design, including system schematic.
• A complete list of components.
• Drawings of major system components, such as nozzles, selector valves, agent storage cylinders or tanks, etc.
• Sample computer program input sheets.
• Sample calculations and drawings for typical system installations in accordance with the applicable vessel regulations (such as 46 CFR 95.15 for cargo vessels) which will enable USCG personnel to verify calculations.

An operator of a subchapter T vessel that is required to install a fixed gas fire extinguishing system has several alternatives.

     The operator may choose a system that will alert him or her to a fire through a fire detection system prior to the operator discharging a manual fixed system

-or-

     The operator may install a completely automatic system that discharges the fixed system upon detection of a fire without any interaction from the operator.

While automatic mechanical ventilation shut-off is required on all custom and pre-engineered fixed gas fire extinguishing systems, an automatic engine shutdown is not. The automatic shutdown of propulsion machinery is only required when the fixed gas fire extinguishing system is activated and when the machinery draws its intake air from within the protected space. However, a dedicated intake air duct to all propulsion machinery from outside the protected space eliminates the need for an automatic engine shut-off switch. The requirement for automatic shut-off switches stems from two facts: that propulsion machinery or mechanical ventilation of the protected space may deplete the extinguishing agent before it is able to perform its function; and that most engine room fires are caused and/or fed by fuel or lubricating oil. An automatic shut-off may also prevent damage to the propulsion machinery from intake of an extinguishing agent and allow an expeditious restart of the propulsion machinery after extinguishing the fire.

The various engine shut-down options available are explained below:

1. If the machinery space of the subchapter T vessel can be protected by the contents of one portable or semi-portable fire extinguisher, such an extinguisher may be used as a fixed gas fire extinguishing system subject to the requirements found in 46 CFR 181.400(b)(5). When installing a fixed system such as this, a fire detecting system per the requirements of 46 CFR 181.400(c) is also needed. This allows for complete manual control of the fixed gas fire extinguishing system by the operator of the vessel. Marking instructions required by 46 CFR 185.612 direct the operator to secure ventilation and machinery prior to the discharge of the fixed system.

2. A custom-engineered fixed gas fire extinguishing system may be installed in a subchapter T vessel in accordance with 46 CFR 181.410. It is installed as a manual system activated by the operator following the indication of a fire from a fire detection system in the protected space. If the propulsion machinery draws intake air from within the protected space, mechanical ventilation is automatically shut off following the fixed system's activation by the operator.

3. A subchapter T vessel operator may install an "off the shelf" pre-engineered system in accordance with 46 CFR 181.420. This system will automatically shutdown propulsion machinery (that draws air from the protected space), and mechanical ventilation without any interaction from the operator. Some manufacturers provide a spring activated manual override switch that permits the operator to maneuver his vessel out of danger before initiating the shutdowns and subsequent discharge of the fixed gas fire extinguishing system.

4. Subchapter T was written assuming that Clean Agents would be the preferred extinguishing agents for these vessels since less of these agents, as opposed to CO2 , is needed to accomplish the same task. The thinking was that most small passenger vessels lacked sufficient space to accommodate CO2 cylinders. Since Clean Agents may be consumed by the engines, depleting the concentration to a point that it would not extinguish a fire, the requirement for an automatic shut down of the engines was included in the regulations. CO2, when ingested by an engine, will shut down the engine effectively serving as a shut down device. Therefore, operators who choose CO2 as the extinguishing agent may forgo the installation of a separate device to shut the engines down. This action may be taken under 46 CFR 175.540 as an equivalency.

Custom engineered systems

These are type approved systems originally intended for manned spaces on large vessels, but include scaled-down system configurations suitable for installation in unmanned spaces such as engine compartments on Subchapter T vessels. They include carbon dioxide systems (approval category 162.038) and new clean fire extinguishing agents such as FM200 and FK-5-1-12 or Novec 1230 (approval category 162.161). There are no new halon systems because halon is no longer manufactured due to environmental concerns.

These systems are type approved after initial testing by an independent testing lab and are described in the manufacturer's approved design, installation, operation and maintenance manual. They are called "engineered" or "custom engineered" because they are specifically designed for each vessel's engine room by amount of agent, pipe lengths, pipe sizes, nozzle size, number of nozzles, etc. The system manufacturer's distributor (not the vessel operator) designs these systems by entering a vessel's engine room dimensions into the manufacturer's computer program, which calculates the amount of agent, number of agent cylinders, pipe sizes, and number and size of nozzles, etc., needed to protect the specific engine room. The system components must be selected from the manufacturer's approved manual.

Manufacturers of custom engineered systems are issued certificates of approval, which can be found on-line at CGMIX.

The review of these systems is conducted primarily by the Coast Guard Marine Safety Center.

Pre-engineered systems

These are type approved systems originally designed for pleasure craft engine compartments as automatic systems, but many models are suitable for many Subchapter T applications because they are equipped with manual backup actuators and provisions for ventilation and engine shutdowns. They are called "pre-engineered" because they are tested by an independent testing lab to extinguish a fire in a simulated engine compartment of the maximum volume which they are intended to protect. Unlike custom engineered systems, a pre-engineered system can be installed in any unmanned engine room of equal or lesser gross volume in accordance with the limitations described in its owner's manual.

The systems are intended to be an "off the shelf" item suitable for installation by either a fire equipment distributor or the vessel's operator. The systems currently type approved are simple, consisting of a single agent cylinder with attached valve, and are attached to a bulkhead inside the engine compartment. Currently approved systems have no discharge piping, the agent being discharged directly from the cylinder valve through the attached sprinkler head when the heat from a fire causes the sprinkler head to actuate. The agents include clean agents FM200, FE241, and FK-5-1-12 (all under approval category 162.029), and carbon dioxide (although no systems are currently being marketed). The systems must be installed and maintained in accordance with the manufacturer's approved owner's manual.

Manufacturers of pre-engineered systems are issued certificates of approval, which can be found on-line at CGMIX.

These system installations are reviewed and approved by the Coast Guard Officer in Charge Marine Inspection (OCMI) on a vessel-by-vessel basis.

Alternatives

If the machinery space of the Subchapter T vessel can be protected by the contents of one portable or semi-portable fire extinguisher, such an extinguisher may be used as a fixed gas fire extinguishing system subject to the requirements found in 46 CFR 181.400(b)(5). However, portable and semi-portable extinguishers may not be converted into fixed systems by replacing components such as valves, hoses and nozzles with miscellaneous valves, piping, etc., for the following reasons:

1. Such modifications void laboratory (Underwriters Laboratories (UL) or Factory Mutual (FM)) listings and Coast Guard type approvals. Also, manufacturers will deny responsibility when injuries occur or the modified equipment does not extinguish a fire.

2. There is no guarantee that the modified equipment will work. Fire extinguishers obtain their UL or FM Listings and CG type approval after undergoing extensive tests and quality control inspections. They're approved as a unit (as they leave the factory). Field modifications do not have the benefit of having undergone such tests.

3. Modifying fire extinguishers is inherently dangerous to the persons doing the modifications because it involves high pressure cylinders (the pressure inside a CO2 extinguisher is 850 psi at 70 degrees F (5900 kPa at 21 degrees C)). That's why DOT requires organizations servicing high pressure cylinders to be DOT certified.

It is possible to use portable and semi-portable extinguishers to flood engine compartments in lieu of using a fixed system by following these guidelines:

A portable extinguisher attached to the outside of the engine compartment can be discharged through a closeable discharge port into the protected compartment. The method of attachment should permit the nozzle to be inserted into the discharge port during a fire. The discharge port must be sized to accommodate the extinguisher nozzle. This procedure is also used on pleasure craft as an (second best) alternative to fixed systems protecting small volumes (American Boat and Yacht Council (ABYC) Standards, Chapter A-4), where a portable fire extinguisher is attached by its bracket next to the discharge port. This concept has been shown to be a viable concept for small engine compartments through tests by ABYC committee members and Coast Guard R&D Report No. CG-D-31-76.

The situation with semi-portable extinguishers (46 CFR 162.039 defines them as extinguishers exceeding 55 pounds (25 kg) in gross weight) is more complex in view of the greater amount of CO2 used (currently up to 100 pounds (45 kg)), and the larger spaces this amount of CO2 can protect.  They are permitted where they can supply the amount of CO2 needed for total flooding as determined by the OCMI. However, to work properly, the nozzles must distribute the agent uniformly throughout the space. For the engineered CO2 systems they are intended to replace, the reach of CO2 from a single nozzle is about 10 feet (3 m). Nozzles for engineered systems are spaced uniformly throughout the space in order to achieve a uniform extinguishing agent concentration. As a result the use of semi-portables (which have only one nozzle) should be limited to situations where a one-nozzle system would suffice, i.e. the distance from the nozzle to the compartment end should not exceed 10 feet (3 m). The volume of the space so protected should therefore be not more than 1000 cubic feet (28 cu m). It is also not acceptable to hang the hose into the protected compartment and rig the spring-loaded valve at the end of the hose to stay open. The rubber hoses and plastic nozzles have not been subjected to any relevant testing and are not expected to withstand a fire exposure.

The semi-portables must not be modified, by replacing valves, hoses and nozzles which are supplied as an integral part of each semi-portable with different valves, fixed pipe, and different nozzles. Any semi-portable systems that have been so modified are to be considered custom-engineered systems and must be specifically approved by the Coast Guard in accordance with 46 CFR 181.410.

In view of the great variety of engine compartment designs and fire protection equipment available it will not be possible to provide specific guidance applicable to all situations encountered in the field. The above may be used as general guidance to be applied to the extent local conditions permit. Unusual situations must be addressed on a vessel-by-vessel basis. For example, where the large and irregular shape of the protected space does not permit the above mentioned nozzle coverage, or where the space has a significant amount of uncloseable openings, additional CO2 may be supplied as compensation to ensure that the CO2 in the space can reach extinguishing concentrations.