Fire alarm system
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General Active fire protection Fire suppression Fire extinguishers Fire detection/alarm Fire alarm control panel Practices |
A fire alarm system is an active fire protection system that controls all the fire alarm components in a building. Fire alarm systems are subject to stringent bounding.
The design of fire alarm systems is required to be performed by competent engineers with experience in fire protection, who are licensed within the geographical area of practice, such as a US State or a Canadian Province. Extensions of existing systems should be done using the original specification for the system and more than likely will be proprietary to match the existing equipment.
A fire alarm system should include, but not be limited to, alarm initiating devices, alarm notification appliances, control units, fire safety control devices, annunciators, power supplies, and wiring.
The A/E should provide a design in compliance with the NFPA fire codes unless a variation is approved. It is recommended that approval come those knowledgeable in fire alarm design.
Fire alarm systems shall comply with requirements of NFPA 72 unless variations to NFPA 72 are specifically identified within these contract documents by the following notation: "variation". The design, system layout, document submittal preparation, and supervision of installation and testing shall be provided by a technician that is certified NICET level III or a registered fire protection engineer. The NICET certified technician shall be on site for the supervision and testing of the system. Factory engineers from the equipment manufacturer, thoroughly familiar and knowledgeable with all equipment utilized, shall provide additional technical support at the site as required by the Contracting Officer or his authorised representative. Installers shall have a minimum of two years experience installing fire alarm systems.
A (DACT) digital alarm communicator transmitter should be connected to a pair of dedicated telephone lines to transmit an alarm signal only to a central station that is responsible for dispatching the fire department. The connection to the fire department is usually via a central station monitoring company that is contracted on a monthly basis by the facility. If a connection to the fire department is not already present, the facility will need to determine if there are two telephone lines available for this connection.
The main fire alarm control unit should automatically transmit alarm signals to a listed central station using a digital alarm communicator transmitter in accordance with NFPA 72.
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[edit] Bounding
The boundaries of the fire alarm system per building should be identified. The following questions are exemplary of what goes into setting up a fire alarm system:
- What buildings are involved in the project; list the specific buildings?
- What interface is there with door magnets?
- What interface is there with the elevator (shut down and recall; speakers in cars)?
- What interface is there with HVAC systems for fan shut down?
- What interface is there with Kitchen Hood suppression systems?
- What interface is there with fire sprinkler systems?
- What interface is there with dry pipe sprinkler systems?
- What interface is there with preaction/deluge systems?
- What interface is there with a fire pump?
- What interface is there with temperature switches for storage tanks and dry pipe valve rooms?
- What interface is there with door locking systems?
- What interface is there with electric eyes (they could open doors upon detection of smoke)?
- What interface is there with fire department?
- What interface is there with the pagers or hand radio system?
- What interface is there with the emergency generators?
- Where is the fire command station?
- Are two-way fire phones to be provided, where?
When fire alarm systems malfunction, they will often produce nuisance alarms.
[edit] Devices
Fire alarm systems have devices connected to them to detect the fire/smoke or to alert the occupants of an emergency. Below is a list of common devices found on a fire alarm.
- Manual pull stations/manual call points - Devices to allow people to manual activate the fire alarm. Usually located near exits.
- Smoke detectors - Spot type: Photoelectric and Ionization; Line type: Projected Beam Smoke Detector; Air-Sampling type: Cloud Chamber
- Water Flow Switches - Detect when water is flowing through the fire sprinkler system
- Rate-of-Rise and Thermostat (heat) Detectors - Detect heat changes
- Valve Position Switch - Indicates that a fire sprinkler system valve that is required to be open, is now closed (off-normal).
- Carbon Monoxide Detectors - Detects poisonous carbon monoxide gas.
- Horns/Strobes - Visual and Audible devices to alert people of system activation.
- Magnetic Door Holder - Doors are allowed to close when the fire alarm is activated.
[edit] Audio evacuation systems
An audio evacuation system or voice evacuation system is a type of fire alarm system. In addition to sirens, horns, or alarm tones, an audio evacuation system plays a voice message with evacuation instructions. These messages can be customized for various types of installations, and multi-lingual capabilities are usually available.
The rationale behind audio evacuation systems is that conventional fire alarms do little more than alert occupants of a building of the presence of an emergency with horns, sirens, and/or strobe lights. They do not give an evacuation route or instructions. The problem lies in buildings where there are a large amount of frequently changing occupants who are not nessacarily familiar with the locations of emergency exits or stairwells. These types of buildings are called "areas of assembly" and are defined as buildings with a capacity of 300 or more people. Areas of assembly include churches, movie theaters, auditoriums, department stores, restaurants, shopping malls, and museums. Additionally, such a system is usually intergrated with a fire telephone or paging system, which permits the fire department or building manager to give specific evacuation instructions pertinent to current conditions in real time.
Many audio evacuation systems permit multiple messages. For instance, "non fire" messages can be programed for situations such as a hazardous material spill, gas leaks, security breaches, severe weather, etc.
In the United States, audio evacuation is now required in many jurisdictions for new structures that are classified as an area of assembly, as well as in new high rise buildings and skyscrapers. Retrofitting older structures is not required, although new fire alarm installations would be required to have audio capabilities. Similar trends are occurring in other countries as well.
