Essentials of Firefighting (4th Edition)
Chapter 15-Fire Detection, Alarm, & Suppression Systems
FF 2 Test Review
The following statements come from the Firefighter II material found on pages 559-571, 578 of this chapter.
§ Local alarm systems, also called protected premises fire alarm systems, are used to notify a building's occupants of the need to evacuate the premises.
§ Fixed-temperature heat detectors operate by expansion of heated material, melting of heated material, and/or changes in resistance of a heated material, and the slowest type of detector to activate.
§ Fusible devices are used to activate a detector by using a piece of solder with a specific melting point.
§ Frangible bulbs hold electrical contacts apart by a glass vial containing a liquid and a small air bubble (the vial breaks when liquid is heated to a specific temperature).
§ Fusible link and Frangible bulb detectors must be replaced since they cannot reset.
§ Continuous line detectors detect heat over a linear area.
§ The ceramic thermistor core of tubing-type continuous line detectors allows a small amount of current to pass from the stainless steel outer tubing to the inner conductor.
§ The heat-sensitive covering on wire actuators of wire-type continuous line detectors allows for completion of the circuit when a specified heat level is reached.
§ Rate of rise detectors are designed to operate when temperature rise of more than 12oF to 15oF occur within a minute.
§ Bimetallic detectors operate by using a metal which arches or bends when exposed to a specified range of heat and in the process completes the circuit of the electrical contacts.
§ Pneumatic rate-of-rise spot detectors operate by allowing air to exit a metering hole during normal atmospheres, yet when the chamber is filled by expanding air from a fire, the detector activates.
§ Pneumatic rate-of-rise line detectors must be limited to about 1,000 feet in length, arranged in rows not more than 30 feet apart, and 15 feet from walls.
§ Rate-compensated detectors are used in areas that are subject to regular temperature changes that are slower than those found with fire.
§ Beam-application photoelectric detectors use a external beam of light (light source) focused across an area onto a photoelectric cell (receiver).
§ Refractory photoelectric detectors use an internal beam of light that passes through a small chamber at a point away from the light source within the device.
§ Ionization smoke detectors use a tiny amount of radioactive material (usually americonium) to ionize materials which enter the chamber of the detector and with smoke or toxic products, the completion of a circuit is created by the charged molecules in the chamber.
§ Photoelectric detectors typically respond faster to smoldering fires than ionization type detectors.
§ Smoke detector batteries should be changed at least every 6 months.
§ Flame detectors detect light from either the infrared wave spectrum, the ultraviolet wave spectrum, or both, and are easily activated by non-fire conditions such as welding, sunlight, and other sources of bright light.
§ Infrared flame detectors are usually installed in fully-enclosed areas since they are sensitive to sunlight.
§ Ultraviolet flame detectors can be used in areas of sunlight, but cannot be used in areas of welding or areas with intense mercury-vapor lamps.
§ Gases released by fires may include: Water vapor (H20), Carbon Dioxide (CO2), Carbon Monoxide (CO), Hydrogen Chloride (HCl), Hydrogen Cyanide (HCN), Hydrogen Fluoride (HF), and Hydrogen Sulfide (H2S).
§ Water vapor, Carbon Dioxide, and Carbon Monoxide are released by ALL fires.
§ Fire-gas detectors are usually faster than heat detectors but slower than smoke detectors.
§ Fire-gas detectors can be used in areas to discriminate between friendly and hostile fires.
§ Combination detectors may include: fixed temperature/rate of rise, heat/smoke, and smoke/fire-gas detectors.
§ Local energy systems are attached to a hard-wired or radio-type municipal fire alarm box which transmits the alarm to the occupancy and to the fire alarm center.
§ A variety of alarm-indicating devices have been developed to accommodate the hearing impaired, work areas with high noise levels, and other alarm tones within a building.
§ Remote station systems are connected directly to the fire department communications center or through an answering service by means other than the municipal fire alarm box system.
§ Proprietary alarm systems are used to protect large commercial and industrial buildings, high rises, and groups of commonly owned buildings.
§ A central station system receives signals from protected properties and re-routes them to the fire department through a direct connection.
§ Auxiliary services of alarms systems may include: shut down or alteration of HVAC systems, closing of smoke or fire-rated doors, elevator override, and/or detecting combustible or toxic gases.
§ Water flow alarms are either hydraulic or electric and are activated by water movement through the sprinkler system.
§ Wet-Pipe Sprinkler Systems are the simplest and easiest to maintain systems.
§ Retard chambers of wet-pipe sprinkler systems catch excess water that may be sent through the alarm valve if water pressure surges.
§ Wet-Pipe sprinkler systems are under (water) pressure at all times.
§ Dry-Pipe sprinkler systems are pitched to promote drainage and have air (20 psi above trip pressure of) in place of water during periods of non-use.
§ Quick-opening devices on dry-pipe systems require a capacity of over 500 gallons.
§ Preaction sprinkler systems consist of a deluge-type valve, fire detection devices, and closed sprinklers.
§ Deluge sprinkler systems are actuated by a deluge valve opened by a signal from a fire detection device.
§ Residential sprinkler systems are designed to prevent total involvement in the room of origin and to allow occupants time to escape.
§ Residential sprinkler systems with fire department connections will have a 1 1/2 inch connection.
§ Residential sprinkler systems may either be tied directly to the public water supply or to the dwelling's domestic supply and must have a pressure gauge, a flow detector, and a means for draining/testing the system.
§ NFPA 13 covers requirements for installation of sprinkler systems.
§ NFPA 13D covers residential sprinkler applications.
§ Inspector's test valves are located in a remote part of a sprinkler system to simulate the activation of one sprinkler.
§ A deluge valve discharges water through every sprinkler connected to the valve.
§ Sprinkler failure is usually due to: partially/fully closed main water control valves, interruption of municipal water supply, damaged/painted-over sprinklers, frozen/broken pipes, excess debris/sediment in pipes, failure of secondary water supply, and tampering/vandalism.
§ Deluge sprinkler systems would most likely be found in modern aircraft hangars.