The Montreal Protocol on Substances That Deplete the Ozone Layer went into effect January 1, 1989. It was an international treaty designed to phase out the production of halogenated hydrocarbons (halon extinguishing agent). Halons are hydrocarbons with one or more hydrogen atoms replaced by atoms from the halogen series (Group VIIA elements from the Periodic Table). The substitution of fluorine, chlorine, bromine, or iodine confers nonflammability and fire extinguishing properties to the agent. Halon-based portable local application (agent is discharged directly onto the fire) extinguishing systems (carbon tetrachloride) have been in use since the early 1900s, when they were introduced. The use of halon-based agents in commercial total-flooding systems (agent stored in tanks, cylinders, or containers and discharged through fixed piping and nozzles/applicators into an enclosed space around the hazard) began in the 1960s. Modern halon agents are highly effective: They leave no residue (clean), are nonelectrically conductive, and have a low toxicity (halon extinguishing systems generally do not release high enough concentrations of halon agents to cause life-threatening effects). They extinguish fire by inhibiting the chemical chain reaction inside the flame zone. Halons are used on Class A, Class B, and Class C fires. Their major drawback, however, is that they contain chlorine or bromine, which are ozone-depleting substances.
The U.S. Army Corps of Engineers devised the numerical system for naming halons without using chemical names. The first digit of the number denotes the number of carbon atoms in the compound molecule; the second digit represents the number of fluorine atoms; the third digit stands for the number of chlorine atoms; the fourth digit, the number of bromine atoms; and the fifth digit, the number of iodine atoms. If the fifth digit is zero, it is not expressed (see Table 1). The phaseout of halon production has had a tremendous impact on the protection of special hazards from fire.
Under the Clean Air Act, the United States banned the production and import of Halon 1211 (local and total flooding agent), Halon 1301 (total flooding agent), and Halon 2402 (a liquid at room temperature used mainly for local application) on January 1, 1994. In the United States, existing halon systems are legal; however, alternative systems have to be provided if the existing halon system is removed or modified. The search for replacement and alternative clean agents is ongoing worldwide.
Clean agents are defined as nontoxic substances generally not hazardous to humans in occupied, enclosed areas when used in lower concentrations (there are limits on the duration of exposure depending on the concentration; there is no acceptable exposure in certain high concentrations). They also do not leave a residue on the contents of the building they are engineered to protect. Clean agents in use today are very effective at extinguishing fire and are fast acting, electrically nonconductive, and economical. They are used in fixed (stationary) total flooding extinguishing systems as well as for fixed and portable local streaming systems. Typical applications for clean agent protection in occupied and unoccupied spaces include aircraft engine nacelles, bank vaults, communications rooms, compressors and pump stations, computer rooms, electrical cabinets, electronics and data processing equipment, flammable liquid storage, gas turbines and diesel generators, historical sites, HVAC control rooms, industrial high-ceiling spaces, kitchens, libraries, locomotives, machinery, military installations, mining equipment, museums and art galleries, offshore drilling rigs, paint spray booths and mixing rooms, petrochemical installations, pharmaceutical and medical facilities, raised floors, record and storage facilities, shipboard and marine engine rooms and holds, telecommunications equipment, and textile plants.
TRADITIONAL CLEAN AGENTS
Carbon dioxide and inert gases are clean agents that have been in use many years and are deemed appropriate as replacements for halon in specified applications. They include the following:
• Carbon dioxide (CO2). A colorless and odorless gas. From 1920 to 1960, it was generally the only gaseous fire extinguishing agent in use. It extinguishes fire by displacing oxygen, thereby eliminating one of the three components of the fire triangle (oxygen, heat energy, and fuel) vital to sustain combustion. CO2 also has a cooling effect on the fire. The high concentration of CO2 (minimum concentration is 34 percent) required to extinguish most fires within enclosed spaces in fixed total flooding systems, however, creates a toxic environment that may be fatal to occupants. The gas is heavier than air and accumulates at floor level like a cloud, impeding and endangering people attempting to escape the area. It is mainly for this reason that carbon dioxide is employed primarily to protect unoccupied buildings or unoccupied spaces (raised floors in computer rooms) in occupied buildings. CO2 works well on Class A, Class B, and Class C fires and also has fixed and portable local streaming uses. When using a portable fire extinguisher, avoid contact with the gas; frostbite is possible.
• Inert gases. They include argon, nitrogen, and helium and are known as the “noble gases” (Group VIIIA elements from the Periodic Table of Elements). These gases are generally nonreactive with other chemical substances. Inert gases are colorless, odorless, and noncorrosive; leave no residue; and are electrically nonconductive. Extinguishing systems using inert gas are designed to reduce the ambient oxygen concentration inside occupied, protected areas from the normal level of 21 percent to as low as 10 percent (with a maximum 3 minute exposure). Within these oxygen limits, occupants can still survive but flaming combustion cannot be supported. Inert gas systems are used to extinguish Class A, Class B, Class C, and some Class D fires.
NEW TECHNOLOGY CLEAN AGENTS
These agents include the following:
• Water mist. These systems incorporate specially engineered fine water spray nozzles that use air to generate a micronized water mist atmosphere. The nozzles can be designed to deliver their spray under low, medium, or high pressures. Water mist systems are more effective than standard sprinkler systems in extinguishing fires. The mist occupies a greater surface area per unit volume of water in comparison with the large water droplets of sprinkler systems.
The enhanced surface area of the droplets allows the water mist to rapidly absorb heat energy from the fire. Additionally, as the water mist droplet changes to steam, it displaces available oxygen in the enclosed environment as it expands to approximately 1,700 times at the base of the fire. Water mist systems use substantially less water (1 gallon/minute/nozzle) to extinguish fire than do standard sprinkler systems (20 gallons/minute/sprinkler head), resulting in less water buildup and damage. Because the water used is deionized and so little water is necessary to extinguish fires, water mist systems surprisingly are designed to safely protect energized electrical equipment. A drawback of water mist is that the air in the room is cooled during the extinguishing process, creating a foggy atmosphere that can impede evacuation procedures. These systems are natural, nontoxic, and highly effective. They are suitable for occupied and unoccupied spaces and have fixed total flooding and portable local streaming uses. Water mist is used on Class A, Class B, and Class C fires.
(2) High-pressure discharge nozzles and stainless-steel piping are two components of water mist fire extinguishing systems.
• INERGEN® (ANSUL). This is a clean agent composed of 52 percent nitrogen, 40 percent argon, and 8 percent carbon dioxide. Its characteristics are similar to those of the inert gases that make up more than 90 percent of this extinguishing agent. Unlike elemental inert gases, however, it elevates the room concentration of carbon dioxide in fixed total flooding systems. The enhanced carbon dioxide atmosphere (4 percent) helps to stimulate deep breathing in the human body (CO2 effect), enabling potentially trapped occupants to breathe acceptable levels of oxygen. Relatively high concentrations of this agent (between 38 and 43 percent) are required in the room or area to be protected. INERGEN® is discharged through nozzles and is used to extinguish Class A, Class B, Class C, and some Class D fires.
• Halocarbon agents. These synthetic organic substances contain a carbon-halogen (chlorine, fluorine, bromine, or iodine) chemical bond individually or in some combination. They are acceptable replacements for the halons. FM-200® (Great Lakes Chemical Corporation) is a common halocarbon agent used widely throughout the world as a replacement for Halon 1301. It is a colorless, liquefied gas that is rapidly fully discharged (within 10 seconds) through nozzles into an area as a clear, nonconductive vapor in fixed total flooding applications. Relatively low concentrations of this agent (between 4 and 9 percent) are required in total flooding systems. FM-200® extinguishes fire by removing heat and inhibiting the chemical chain reaction (fire tetrahedron) inside the flame zone. It is a clean agent that has acceptable toxicity for use in occupied spaces and is effective on Class A, Class B, and Class C fires.
Other common halocarbon agents are trade name FE-25TM (DuPont), which mirrors the fire extinguishing capabilities of Halon 1301 in fixed total flooding systems. It is generally used in concentrations ranging from 8 to 12 percent. Fire protection engineers consider it a “drop-in” replacement for halon extinguishing systems. The agent is also used for explosion suppression (grain elevators).
FE-13TM (DuPont) is ideal for cold temperature areas because of its high boiling point and high vapor pressure. Whereas the effectiveness of FM-200® in an enclosed space is limited to 12-foot nozzle heights, FE-13TM can be discharged from nozzles at ceiling heights up to 25 feet. It can also make atmospheres inside occupied spaces inert.
FE-36TM (DuPont), a replacement for Halon 1211, is a recognized name in portable local application fire extinguishing equipment. It discharges from the extinguisher as a liquid within a range up to 16 feet. It has a very low toxicity level, is noncorrosive, is electrically nonconductive, and leaves no residue. FE-25TM, FE-13TM, and FE-36TM are effective on Class A, Class B, and Class C fires.
• Fluoroketone-type materials. These liquids have low to moderate boiling points that are compressed and pressurized in fire system storage tanks. The liquid is readily vaporized on nozzle discharge.
NovecTM 1230 (3M) is one fluoroketone material. It has fixed total flooding system and fixed/portable local applications. This agent has the widest margin for safety when used in fixed total flooding systems protecting occupied spaces, since its designed concentration is between 4 and 6 percent. It extinguishes Class A, Class B, and Class C fires through its cooling effect.
• Powdered aerosols. These agents technically are not considered clean agents because they leave some residue after discharge. The systems were first introduced in the fire suppression market during the early 1990s. The aerosol consists of up to 40 percent dry powder extinguishing agent (potassium) and 60 percent gaseous molecules (carbon dioxide, nitrogen, oxygen) contained in modular units (box-like generators with discharge outlets or applicators of various sizes in a loop configuration) around an enclosure. Electrical impulse activation from a separate alarm system or a self-contained detection element provides the catalyst. This energy penetrates into the powder/gas mixture, pulverizing the powder and dispersing the agent rapidly (0.1-1 second) over long distances into the area being protected. The small particle size (1-2 micron) of the powder and enhanced surface area allow the dry powder agent to very effectively inhibit the chemical chain reaction inside the fire zone.
Powdered aerosol systems involve simple installation, need negligible maintenance, require no pressurized cylinders or piping, are cost effective, and have proved to have minimal toxic effects on humans. They are used primarily as fixed total flooding systems for enclosed areas. The systems provide highly efficient fire extinguishment of Class A, Class B, and Class C fires for military, industrial, and commercial applications.
FIRE SAFETY AND FIRE PREVENTION RECOMMENDATIONS
Requirements and recommendations for using clean extinguishing agent total flooding systems are contained in National Fire Protection Association (NFPA) 12, Standard on Carbon Dioxide Extinguishing Systems; NFPA 75, Standard for the Protection of Information Technology Equipment; NFPA 750, Standard on Water Mist Fire Protection Systems; NFPA 2001, Standard on Clean Agent Fire Extinguishing Systems; Factory Mutual (FM) 5-32, Electronic Data Processing Systems (smoke detectors); Occupational Safety and Health Administration (OSHA) 29 Code of Federal Regulations (CFR) 1910.160, “Fixed Extinguishing Systems, General” and 1910.162, “Fixed Extinguishing Systems, Gaseous Agents”; and the U.S. Environmental Protection Agency Significant New Alternatives Policy (SNAP) program, Section 612, “Clean Air Act Amendments.”
INSPECTING AND DRILLING ON SYSTEMS USING CLEAN AGENTS
Following are some questions you should ask when inspecting occupancies with fixed total flooding systems using clean agents and when conducting department familiarization drills on these systems.
- Are all air-handling mechanisms automatically disconnected/shut down on activation of the system?
- Is all electronic equipment automatically disconnected/shut down on activation of the system?
- Are employees being trained relative to the type of system installed, hazards, activation procedures, the proper response to alarms, and evacuation?
- Are factory-charged nonrefillable containers being weighed semiannually?
- Are inspection and maintenance dates for the system being recorded, and are they available for examination?
- Is the system inspected annually to ensure operational performance?
- Are operating instructions for the manually discharged devices posted at the station?
- Is a material safety data sheet (MSDS), if required, for the extinguishing agent available at the workplace?
- Are there audible and strobe-light alarms to warn occupants of pending and actual discharge of the agent?
- Are there enhanced (low-level) exit signs to aid in evacuation?
- Are warning/caution signs posted at the entrance to and inside the protected area to warn employees and occupants in advance about any hazards associated with the agent?
- Is an adequate ventilation system installed?
- Is personal protective equipment (air escape packs/hoods) readily available for rescuing employees and occupants trapped in protected areas?
- Is the employer taking effective precautions so that employees are warned when the atmosphere inside the protected area remains hazardous to safety and health after the system has discharged?
- Is the system addressed in an Emergency Action Plan/Fire Safety Plan for each area protected?
- Is the system automatically activated by an approved method of detection?
- Are the weight and pressure of refillable agent storage containers (high/low pressure cylinders/tanks) checked semiannually?
- Is there a control panel to monitor and integrate all components of the system?
- Is a manually discharged device clearly visible (generally mounted to an adjacent wall) at the emergency exit?
- Is there a time delay activation of the clean agent to allow for the safe evacuation of occupants in the area being protected?
- Is there annual training of employees who inspect, maintain, operate, or fix the extinguishing system?
- Is there any effect on human survival within the enclosure the agent protects?
This article is an introduction to halon extinguishing agent alternatives. The materials listed above are just a few of the most popular agents on the market. The ideal clean agent alternative still has not been manufactured. It is the job of the fire protection engineer to preplan the life hazard, if any; the area to be covered; the material/equipment to be protected; the container/cylinder storage space; and the compatible clean agent to be used, as well as many other factors. It is also wise for firefighters to look for and become familiar with these clean agents during drills and building inspections. This knowledge will enhance operational strategy at fires and emergencies. Alternative clean agent extinguishing systems are becoming more and more prevalent. It is important that chief officers and firefighters know where these systems are located, the type of building and occupancy use, how they work, safety precautions that must be taken, and the hazards involved.
Technical Advisory Bulletin – Halon Alternatives, Willis Property Risk Control, February 2005, www.willis.com/news/Publications/Feb2005_Technical_Advisory_Bulletin_Halon.pdf.
“Halon Alternatives – SFE (Powdered Aerosol A),” Spectrex Inc., http://www.spectrex-inc.com/extinguishing/HalonAlternatives.htm/.
“Pollution Prevention Fact Sheet #14: Alternatives to Halon & Other Halocarbon Fire Extinguishing Agents,” Environment Canada, Ontario Region-Environmental Protection Branch, Federal Programs Division, December 2000. http://www.p2pays.org/ref/19/18382.pdf/.
Ronald R. Spadafora is a deputy assistant chief with the Fire Department of New York and an adjunct professor of fire science in the Department of Public Management at John Jay College and CUNY and is a senior instructor for Fire Technology Incorporated. He has an MPS degree in criminal justice from LIU-C.W. Post Center, a B.S. degree in fire science from John Jay College, and a B.A. degree in health education from Queens College, CUNY. He is an editor and frequent contributor to WNYF magazine.