Courtesy of PennState Extension
The best barn fire prevention systems incorporate building design, early warning devices, and fire suppression mechanisms. Building design for fire prevention changes the environment to minimize the spread of heat and flames and provides multiple options for escape. Barn design should increase the time it takes a fire to reach the flash point by modifying ceiling height or room volume, building materials, and building contents.
Although not a common practice horse barns, one way to slow a fire’s spread is to compartmentalize the structure. Compartmentalization divides the stable into “rooms” not longer than 150 feet with fire-resistant barriers such as walls, doors, or fire curtains. This prevents the spread of fire within the building and allows more time for fire suppression. A true firewall must be completely sealed in a fire and should provide at least one hour of fire protection. Any doors in the wall need to be fire-rated and self-closing, and any openings for wiring or pipes need to be sealed. In a stable with a frame constructed roof, the wall itself needs to extend at least 18 inches above the roof; the higher the wall extends, the longer the fire protection. Fire curtains or fire barriers are walls that divide up the open space in the roof trusses and prevent the spread of heat and smoke through the attic space. This prevents the truss area from becoming a natural tunnel for heat and flame travel. Building design determines the size of the fire curtain; the taller the fire curtain, the greater the effectiveness.
Compartmentalization is not as simple as just adding a wall. Preventing the exchange and redirection of superheated air and flame is the operating principle of a firewall or curtain. Although if not properly installed, it disrupts the everyday air patterns needed for proper ventilation in the stable. An option more common at horse facilities is to “compartmentalize” by having entirely separate structures rather than dividing up one extra large building. This is one reason why many racetracks have several modest-sized stables rather than one huge stable.
Proper ventilation will also improve survival by removing gases from occupied areas, directing flow of air currents and fire spread, and providing for the release of unburned gases before ignition. Roof vents are an effective way to ventilate a barn during a fire. Recommendations for vent spacing and sizes are set by the National Fire Protection Association, based on building material types and area to be vented. The most important factor to determine the space needed between vents is the rate at which burning material gives off heat. Horse barn fires burn with moderate- to-high heat production. Stables should have 1 square foot of ceiling vent space for every 100 square feet of floor area. Buildings with hay storage need 1 square foot for every 30 to 50 square feet of floor area. Options include a continuous slot opening along the ridge; roof vent monitors with louvers or thin glass that are opened by the super-heated air; and unit vents that are designed to melt, collapse, or spring open at predetermined temperatures. Each of these vents increases gas removal during the fire. Vents on heat-triggered fuses (usually set to open at 212oF) may not open unless a hot, free-burning fire produces smoke temperatures high enough to activate fuses. This may mean that the fire has had time to progress, depending on its origin. Do not assume that just because vents are installed, the environment within a burning barn is livable. A smoldering fire can produce enough toxic smoke to be an immediate threat to human and animal life.
Fire Detection Devices and Principles
Early warning devices can be an effective tool in fire detection but few are suitable for barn use. In some situations, the main goal is to save the animals housed in the barn, but in other situations, minimizing property damage is the priority. Many early detection and fire suppression systems are available, but most were developed for residential use. This severely limits their practicality in horse or livestock facilities since they tend to be dustier, more humid, and colder than residential environments. It is best to seek advice and recommendations from fire engineers or fire protection professionals familiar with the unique needs and situations found in horse facilities. If you have trouble locating fire protection professionals, contact your fire department and ask for referrals.
Early warning devices were developed to mimic human senses. There are three basic types of fire detection devices: smoke, thermal (heat), and flame detectors. Smoke detectors mimic the human sense of smell. An ionization detector charges the air within the detector so that it will carry an electric current and any resistance to the electrical current will set off an alarm. Smoke particles and dust will interrupt the air’s ability to conduct electrical current. An ionization detector is more responsive to a flaming fire than a smoldering one. For earlier smoke detection a photoelectric smoke detector is recommended. Within a chamber in the smoke detector, is a light-sensitive photocell. Smoke particles and dust will act like miniature mirrors, scattering a light beam and directing it towards the photocell. Once the amount of light detected by the photocell reaches a predetermined point, the alarm is activated.
Smoke detectors are the best line of defense for early warning of fires. They identify the fire while it is in the smoldering or early flame stages. Smoke detectors are not as reliable in the dusty and humid environment of horse barns. Airborne dust and dander or humidity may trigger false alarms. In more controlled environments, such as a lounge or office, a smoke detector is better suited.
Thermal detectors, developed in the mid-1800s, are the oldest type of automatic detection device. They are inexpensive to install and easy to maintain. The most common thermal detectors are fixed temperature devices, set to operate when temperatures reach a predetermined level, usually 135 to 165oF. Another class of thermal detectors, called rate-of- rise detectors, activates an alarm when the temperature climbs at an abnormally fast rate. Both fixed temperature and rate-of-rise detectors are spot detectors and activate sooner with a closer proximity to the heat source.
A third type of thermal detector, the fixed temperature line detector, does not require the sensor to be as close to the heat source for activation. Two wires are run between detectors. Alarms are activated when the insulators, designed to degrade at a specific temperature, are damaged. The benefit of this fixed temperature line sensor is that floor area coverage can be increased at a lower cost. Thermal detectors are highly reliable and are not as affected by a dusty, moist environment. However, their adequacy in a horse barn is debatable since they require the fire to be in the later stages of progression before the sensor recognizes and signals the alarm. The longer a fire has to develop, the greater damage it can cause and the more difficult it is to control, especially in a barn. This is why they are usually not permitted as the sole detection device in life safety applications, such as in residential use.
The most reliable and expensive early warning detection device is the flame detector. These sensors imitate human sight and are most commonly used in aircraft maintenance facilities, refineries, and mines. As with other spot detectors, flame detectors must be “looking” directly at the fire source. Flames are classified by short wavelengths of electromagnetic radiation flickering in the range of 5 to 30 cycles per second. When the device senses these conditions, it is preset to monitor the source for a few seconds, before sounding the alarm. By recognizing the flame’s wavelength, cycle, and consistency, flame detectors differentiate between hot objects and actual fires, minimizing false alarms. The greater the distance the flame is from the sensor, the larger it must be before the sensor will respond to it. They are highly reliable early detection devices especially for hot burning fires that are not likely to give off smoke, such as alcohol or methane fires.
Early warning systems can add valuable time to rescue efforts, if someone is available to hear them. One way to ensure that someone is alerted when a fire is detected is through a telephone dialer. A telephone dialer provides 24-hour alarm monitoring. The dialer can be connected to a professional monitoring service, family, neighbors, or directly to the fire department. It may be best to alert someone near the premises first, to prevent calling the fire department for any false alarms. However, best judgement should prevail, and if the nearest neighbor is too far away, contacting the 911 operator may be a better alternative. A phone dialer will need its own line, to ensure the availability of a phone connection after a fire has been detected.
Automatic Fire Suppression
Sprinkler systems are an effective tool for controlling fires but are not common in rural horse barns. Most sprinkler systems open to apply water to a fire when a sensing element in the individual sprinkler head comes in contact with intense heat. Only the sprinkler heads that come in contact with the fire’s heat react, minimizing the water needed to extinguish the fire. A sprinkler system usually suppresses a fire with as few as two sprinkler heads and is very effective at controlling fires before they get out of hand. However, for sprinkler systems to be effective, an adequate water supply needs to be available at all times to provide enough gallons and sufficient pressure to extinguish the fire. It is often difficult for rural horse farms to meet these criteria. On average, one sprinkler head will deliver 25 gallons of water per minute to extinguish the blaze. As more sprinklers are activated, more water must be available to maintain pressure in the line (47 gallons and 72 gallons per minute for activation of the second and third sprinklers, respectively.) If water availability is a problem, a tank can be installed. This is an extremely expensive addition that will need regular service checks and maintenance.
If the facility’s water supply is sufficient, several options are available for sprinkler systems. A sprinkler system that holds water all the time is called a wet-pipe system. These are the most inexpensive systems to install and require the least amount of maintenance. However, in climates where the barn temperature is too low to prevent freezing, the wet-pipe system will not work.
In freezing environments, a dry pipe system is employed. The supply lines are pressurized with air or nitrogen gas to hold a valve closed, preventing water from entering the system. In a fire, the sprinklers are activated, releasing the pressure and opening the valve. If the pressure is released through damage to the supply line, the valve is also released. This poses problems if the valve release is not found and temperatures are low enough for freezing to occur. Dry-pipe systems are more limited in design. The reliance on pressure to close a valve creates strict requirements on the overall size and locations of the sprinkler heads and sup- ply lines. The increased system complexity requires more components, has more opportunity for failure, and increases the costs of installation and maintenance.
A preaction system was designed to eliminate the danger of accidental valve release on the dry-pipe system. A preaction system uses an electronically operated valve to prevent water from prematurely entering the pipes. In order for the valves to be opened, an independent flame, heat, or smoke detection device must identify a fire or potential fire. Once a fire is detected, the valve is released and the water is available to the sprinkler heads. The sprinklers open when triggered by heat, not by the valve detection device. As with an increasingly complex system, installation and maintenance costs increase along with the potential for malfunction.
One promising technology for areas with limited water supplies is the water mist. This system was originally designed for controlling severe fires on ships and oil-drilling platforms, where excessive water use could make the vessel capsize. Currently, these systems are standard on marine vessels, and have a proven record of extinguishing maritime fires. Their applications in buildings have been recognized and used in Europe. Water mist systems are highly pressurized, ranging from 100 to 1,000 psi and produce finer droplets 50 to 200 microns in diameter (sprinklers deliver 600 to 1,000 micron droplets). These smaller droplets are exceptionally efficient at cooling and fire control with 10 to 25 percent less water than a sprinkler system. Due to its limited availability, this technology is significantly more expensive than sprinkler systems. Currently, insurance companies do not recognize water mist systems as a fire suppression system and will not give rate incentives for them. Recognition of and advancements in this technology should bring it closer to affordable horse farm applications.