Fire Detection Systems and Alarms
Although smoke detectors save lives and protect property by giving early warnings of fire, the most effective fire prevention method is automatic fire sprinklers.
Almost 90 percent of fires are extinguished by the discharge of one or two heads, or about 40 gallons of water compared to 150 to 250 gallons a minute of discharge by fire hoses. Less than 10 percent of residential fires require the activation of four or more sprinkler heads.
Most fires are suppressed within seconds, usually with no more than one or two sprinkler heads being activated.
In buildings with sprinkler systems that had fires, the sprinkler systems extinguished the blaze in 65 percent of the cases and in 32 percent of the cases; the sprinklers contained the fire until other firefighting measures could be taken.
Types of Fire Suppression Systems
- Wet pipe
- Dry pipe
- Pre-action dry pipe
- Deluge systems
- Gaseous Agents
- Ansul dry chemical
Wet Pipe
Wet pipe systems are the most common fire sprinkler system. A wet pipe system is one in which water is constantly maintained within the sprinkler piping. When a sprinkler activates, this water is immediately discharged onto the fire.
Dry Pipe
A dry pipe sprinkler system is one in which pipes are filled with pressurized air or nitrogen, rather than water. This air holds a remote valve, known as a dry pipe valve, in a closed position. Located in a heated space, the dry-pipe valve prevents water from entering the pipe until a fire causes one or more sprinklers to operate. Once this happens, the air escapes and the dry pipe valve releases. Water then enters the pipe, flowing through open sprinklers onto the fire.
Pre-action Dry Pipe
Pre-action fire sprinkler systems employ the basic concept of a dry pipe system in that water is not normally contained within the pipes. The difference, however, is that water is held from piping by an electrically operated valve, known as a pre-action valve. Valve operation is controlled by independent flame, heat, or smoke detection.
Deluge Systems
A deluge system is similar to a pre-action system except the sprinkler heads are open and the pipe is not pressurized with air. Deluge systems are connected to a water supply through a deluge valve that is opened by the operation of a smoke or heat detection system. The detection system is installed in the same area as the sprinklers. When the detection system is activated water discharges through all of the sprinkler heads in the system. Deluge systems are used in places that are considered high hazard areas such as power plants, aircraft hangars and chemical storage or processing facilities.
Gaseous Agents
Critical to the functioning of the system is the fire detection and control network. Typically smoke detectors sense the presence of fire in the protected facility. The detection and control panel then sounds an alarm, shuts down air handlers, disconnects power from the protected equipment, and then releases agent into the protected area.
Halon 1301
Halon 1301 systems are commonly found in computer room applications. The Halon 1301 agent is no longer manufactured. The United States Environmental Protection Agency (EPA) has mandated the phase out of all new Halon 1301 production as of December 31, 1993.
- If you have Halon systems currently installed there is no legal obligation to remove systems from service.
- You may legally recharge your system in the event of a discharge.
- Recycled agent is still commonly available for fire system recharge.
- You should plan on replacement of the systems eventually with a Halon alternative.
Halon 1301 Substitute Systems (FM 200 & Inergen)
Inergen
Inergen is a blend of three naturally occurring gases--Nitrogen, Argon, and Carbon Dioxide. An Inergen system lowers the oxygen content of the protected area to a point sufficient to sustain human life, but insufficient to support combustion. Because it's not a chemical agent, Inergen will not produce a heavy fog the way other extinguishing agents do, so escape routes remain visible.
FM 200
FM-200 chemically known, as heptafluoropropane is an alternative fire suppression system agent manufactured in the United States by Great Lakes Chemical (FM-200) and is a replacement for the ozone depleting Halon 1301 used extensively before 1994. FM-200 has found by leading toxicologists to be safe for use when people are present. Just as with Halon 1301, people can be exposed to normal extinguishing concentrations of without any fear of health problems
Ansul dry chemical
The Ansul system is actuated by fusible links located above the cooking appliances. The links melt during a fire, causing cartridge to fire propelling gas into the Ansulex liquid agent tank. The distribution piping system carries the agent to nozzles located above the cooking appliances, in the plenum above the filters, and in the duct above the plenum.
This section applies to all automatic sprinkler systems installed to meet a particular OSHA standard.
- For automatic sprinkler systems used to meet OSHA requirements and installed prior to the effective date of this standard, compliance with the National Fire Protection Association (NFPA) or the National Board of Fire Underwriters (NBFU) standard in effect at the time of the system's installation will be acceptable as compliance with this section.
- All automatic sprinkler designs shall provide the necessary discharge patterns, densities, and water flow characteristics for complete coverage in a particular workplace or zoned subdivision of the workplace.
- The employer shall assure that only approved equipment and devices are used in the design and installation of automatic sprinkler systems used to comply with this standard.
Maintenance.
- The employer shall properly maintain an automatic sprinkler system installed to comply with this section. The employer shall assure that a main drain flow test is performed on each system annually. The inspector's test valve shall be opened at least every two years to assure that the sprinkler system operates properly.
Acceptance tests.
- The employer shall conduct proper acceptance tests on sprinkler systems installed for employee protection after January 1, 1981, and record the dates of such tests.
- Proper acceptance tests include the following:
- Flushing of underground connections;
- Hydrostatic tests of piping in system;
- Air tests in dry-pipe systems;
- Dry-pipe valve operation; and
- Test of drainage facilities.
Water supplies .
- The employer shall assure that every automatic sprinkler system is provided with at least one automatic water supply capable of providing design water flow for at least 30 minutes. An auxiliary water supply or equivalent protection shall be provided when the automatic water supply is out of service, except for systems of 20 or fewer sprinklers.
Hose connections for fire fighting use .
- The employer may attach hose connections for fire fighting use to wet pipe sprinkler systems provided that the water supply satisfies the combined design demand for sprinklers and standpipes.
Protection of piping.
- The employer shall assure that automatic sprinkler system piping is protected against freezing and exterior surface corrosion.
Drainage .
- The employer shall assure that all dry sprinkler pipes and fittings are installed so that the system may be totally drained.
Sprinklers
- The employer shall assure that only approved sprinklers are used on systems.
- The employer may not use older style sprinklers to replace standard sprinklers without a complete engineering review of the altered part of the system.
- The employer shall assure that sprinklers are protected from mechanical damage.
Sprinkler alarms.
On all sprinkler systems having more than twenty (20) sprinklers, the employer shall assure that a local waterflow alarm is provided which sounds an audible signal on the premises upon water flow through the system equal to the flow from a single sprinkler.
Sprinkler spacing.
- The employer shall assure that sprinklers are spaced to provide a maximum protection area per sprinkler, a minimum of interference to the discharge pattern by building or structural members or building contents and suitable sensitivity to possible fire hazards.
The minimum vertical clearance between sprinklers and material below shall be 18 inches (45.7 cm).
Hydraulically designed systems .
- The employer shall assure that hydraulically designed automatic sprinkler systems or portions thereof are identified and that the location, number of sprinklers in the hydraulically designed section, and the basis of the design is indicated.
Alarms Systems
General requirements.
- Alarm system shall provide warning for necessary emergency action as called for in the emergency action plan, or for reaction time for safe escape of employees from the workplace or the immediate work area, or both.
- The employee alarm shall be capable of being perceived above ambient noise or light levels by all employees in the affected portions of the workplace.
- The employee alarm shall be distinctive and recognizable as a signal to evacuate the work area or to perform actions designated under the emergency action plan.
- The employer shall explain to each employee the preferred means of reporting emergencies, such as manual pull box alarms, public address systems, radio or telephones.
- The employer shall post emergency telephone numbers near telephones, or employee notice boards, and other conspicuous locations when telephones serve as a means of reporting emergencies. Where a communication system also serves as the employee alarm system, all emergency messages shall have priority over all non-emergency messages.
Installation and restoration.
- The employer shall assure that all devices, components, combinations of devices or systems constructed and installed to comply with this standard are approved. Steam whistles, air horns, strobe lights or similar lighting devices, or tactile devices meeting the requirements of this section are considered to meet this requirement for approval.
- The employer shall assure that all employee alarm systems are restored to normal operating condition as promptly as possible after each test or alarm. Spare alarm devices and components subject to wear or destruction shall be available in sufficient quantities and locations for prompt restoration of the system.
Maintenance and testing.
- The employer shall assure that all employee alarm systems are maintained in operating condition except when undergoing repairs or maintenance.
- The employer shall assure that a test of the reliability and adequacy of non-supervised employee alarm systems is made every two months. A different actuation device shall be used in each test of a multi-actuation device system so that no individual device is used for two consecutive tests.
- The employer shall maintain or replace power supplies as often as is necessary to assure a fully operational condition. Back-up means of alarm, such as employee runners or telephones, shall be provided when systems are out of service.
- The employer shall assure that all supervised employee alarm systems are tested at least annually for reliability and adequacy.
- The employer shall assure that the servicing, maintenance and testing of employee alarms are done by persons trained in the designed operation and functions necessary for reliable and safe operation of the system.
- Manual operation. The employer shall assure that manually operated actuation devices for use in conjunction with employee alarms are unobstructed, conspicuous and readily accessible.
