Fire alarm systems perform several functions that limit loss of life and property loss during a fire. They provide smoke and fire detection with warnings for evacuation, and notification for fire department response.
Alarm Initiating Devices: Manual Fire Alarm Pull Boxes, Waterflow Initiating Devices, Heat and Smoke Detectors.
Notification Appliances: Bells, Horns, Speakers, Sirens, Strobes, Voice Commands.
FDC's, NFPA STANDARDS FOR STANDPIPES/SPRINKLERS
TIP: High-rise buildings and Malls are required to provide manual controls for AHU equipment so that Firemen can use it to ventilate the structure.
TIP: AHU's (Air Handling Units) over 2000 CFM must automatically shut down upon activation of a duct smoke detector installed upstream from an AHU.
TIP:Smoke detectors are required in lobbies to ensure the elevators do not return to fire floor.
TIP:Most fire protection systems require monitoring to prevent tampering.
TYPES OF SPRINKLER SYSTEMS:
WET PIPE: The most common type of sprinkler system. Water is kept under constant pressure throughout the pipes and releases when a heat activated sprinkler head opens.
DRY PIPE: Air in the pipes under pressure replaces water to protect against freezing temperatures. These are common in outdoor facilities like parking garages. (The pump room has to be heated)
PREACTION: Basically a combination of a wet and dry system. Water is not kept in the pipes and doesn't flow unless signaled by a separate detection device. Then water will flow and fill the pipes up with water to the sprinkler head until that activates. Preactions are common in museums, libraries and computer rooms to prevent water damage where expensive equipment and historical documents are stored.
DELUGE SYSTEM CLICK HERE.
WATER FLOW DEVICES: Installed on automatic sprinkler systems to provide an alarm when the system activates. Detects water flow in the sprinkler system, which then sends a signal to the alarm panel. Water pressure switches operate when the flow of water moves a mechanical operator such as a paddle. Water flow switches have a retard feature that holds the alarm for a set period of time during pressure changes and water surges, which prevents unwanted alarms from occurring. False alarms also occur when retard chamber drains become clogged preventing water from draining from the chamber, reducing its function.
PULL STATIONS: There are two basic types of manual pull stations: single-action and double-action. The single only requires one action to activate. The double requires two actions, one to gain access to the device and another action to actually activate it.
There several different ways to reset pull stations. The Simplex (L) resets with a key by just opening it and closing it. The Edwards (C) requires a flathead screwdriver to open, then toggle switch has to be reset. The problem with these are stripped heads on the screw.
The fire call pull box (R) has been phased out and disabled in most cities due to multiple MFA's, but a few cities still use them. The pull station has to be reset in order to reset the alarm (unless zone disabled).
Fire Protection Systems: There are many types of fire protection systems that fire departments deal with regularly. It's important that all firemen and not just company officers have some basic knowledge of the more common types of protective systems they will be dealing with throughout their careers. They include residential and commercial smoke, heat, duct and CO detectors, pull stations, sprinklers, standpipes, deluge systems, fire extinguishers, elevator recall, automatic closing doors, call boxes, standpipes, fire pumps, smoke towers, hvac smoke control and smoke removal systems.
ALARM SYSTEMS: Fire alarms operate in one of three states; Normal, Alarm and Trouble. Having basic knowledge of these systems and their operation will make alarm activations much easier to mitigate.
Fire Protective Systems are broken down into alerting systems, suppression systems and auxiliary functions.
ALERTING SYSTEMS: Smoke detectors, alarm activations with strobe lights and audible devices sounding are examples of alerting devices.
SUPPRESSION SYSTEMS: Sprinklers, fire pumps, deluge systems, fire extinguishers, FDC connections and standpipes are suppression systems.
AUXILIARY FUNCTIONS: Elevator recall, automatic shutdown of HVAC/AHU, smoke removal exhaust systems, stairwell pressurization systems, de-magnetizing or release of fire/smoke doors and alarms notifying central station monitoring companies/fire departments are auxiliary functions.
INTITIATING DEVICES: Capable of placing the system in the alarm state. Manually activated devices such as manual pull stations, break glass boxes, call points and pull boxes. Automatic devices would include heat/smoke/flame detectors, elevator recall, door releases and AHU shutdown.
WATERFLOW ALARM: Water flow sensors are located at fire sprinkler riser pipe and triggers when water flows through the pipe when a sprinkler head activates.
FIRE ALARMS: When receiving an alarm activation, the first arriving company reports to the annunciator or main fire alarm panel to see what it's indicating. This indication will usually give the type of alarm and its exact location or a zone. If the alarm is a digital addressable initiating device, the panel will indicate the area and which device activated the alarm (smoke detector, pull station, heat/flame detector, tamper switch).
Annunciator panels are usually near the main entrance of the building or security area, and indicate the type of alarm and its location. The main control panel is usually in another location inside of a locked room or office. From there you can silence, reset the alarm and control the system. (Some alarms can be reset and operated by the annunciator panel) The annunciator panel will indicate what type of alarm as soon as you enter the building most of the time. The most common are:
GENERAL: An alarm condition exists- smoke/heat detector, sprinkler flow switch, pull station, and an audible alarm/flashing strobes activated.
TROUBLE: A trouble condition exists on the panel when a zone or indicator is disabled, a smoke head is contaminated, or there's an electric problem in the system.
SUPERVISORY: Part of the buildings fire protection system has been disabled, tamper switches deactivated or sprinkler control valves closed. CO detectors and duct detectors transmitted to a fire alarm system shall be permitted to be supervisory signals.
FIRE SUPPRESSION SYSTEMS: Many commercial kitchens in restaurants, stadiums, schools, office buildings and cafeterias have suppression systems, mainly in the hood area. Service stations with fueling pumps also have overhead automatic fire suppression systems. They can be automatic or manually activated. Carbon Dioxide, Halon and Argon are common agents used in these systems.
When arriving at a kitchen fire in a commercial building, make sure the suppression system has been activated. If not, look for a red button on the wall nearby, remote from the cooking area and manually activate it if it can be done safely.
SPRINKLERS: Sprinklers are activated by release mechanisms when exposed to fire/heat. The three most common heat mechanisms are fusible link, glass bulb and chemical pellet. Sprinklers are capable of anywhere between 25-150 GPM. Residential and small office sprinklers are usually 25-40 GPM. while commercial buildings/warehouses are closer to 75-100. RESPONDING TO ACTIVATED SPRINKLER SYSTEMS- CLICK HERE
SMOKE DETECTORS: Most residential homes in America use Ionization and photoelectric type smoke detectors. Both are reliable but can cause false alarms due to minor cooking, steam from a shower and dust build up.
CO/SMOKE COMBINATION DETECTORS: These newer devices may cause some confusion for occupants on determining whether it's a smoke or a carbon monoxide alarm. The occupants call the fire department suspecting the smoke detector is sounding when it's the CO alarm. Some combination alarms are voice actuated or have a number of beeps or lighting to identify which alarm is activated. Take the head down and read the label if not sure and take CO readings as aprecaution.
AIR DUCT SMOKE DETECTORS: Operates on smoke detector technology and detects smoke for the primary purpose of controlling the propagation of smoke through the HVAC. These detectors only detect smoke when it's circulating in the duct. Air duct detectors are located within the ducts or on the ducts with an airflow sensor (tube) inside the duct. Duct detectors are not a substitute for area smoke detectors or a buildings regular fire detection system. It helps prevent possible panic from distribution of smoke through the HVAC system. They are sometimes difficult to locate as they are installed behind ceilings or mechanical rooms. Upon activation, a remote indicator with a steady red light can usually be located on the ceiling or wall nearby. They are subject to false alarms due to dust and humidity and are required to transmit a supervisory alarm, not a fire signal (unless they are programmed to transmit a fire alarm).
HEAT DETECTORS: Work on two basic principles: fixed temperature and rate of rise. (Some have both) Enclosed areas (rooms, closets), used for property protection requiring a more sensitive heat detection. NOT considered an early warning device. May be located on ceilings in mechanical areas and other spaces subject to dust, debris and heat.