Fire systems are designed for different services such as to warn people of fires, to stop fires, to create a safe environment for people in a fire among other reasons. The installation of these system depends on the buildings and occupants or the kind of materials in the buildings such as flammable liquids or electronic devices. The selection of these systems should meet the set standards by the different fire-related organisations. The following is a look at some of the fire and prevention systems.
Standpipe System
Standpipe systems are a number of pipes that connect a water supply to hose connections. The system is designed to provide pre-piped water for a building’s occupants or to the fire department. Some buildings only have standpipes while newer buildings include other combinations of fire prevention systems. The system is common in large buildings where the building is away from the outside entrance. The standpipe system has three classes. Class I provides a 2 ½ inch connection used by trained persons or the fire department. There are no hoses attached for this class. The fire department carries hose packs to the floor where they connect to the system and start their operations. Class II provide 1 ½ inch hoses to connect to a water supply also used by trained people or the fire department. The class is typically found in a cabinet with 100-inch hose. Class III has a 1 ½ inch hose station and a 2 ½ hose connection to a water supply (Mettauer, 2007).
The International Fire Code, International Building Code and NFPA 101 require the use of standpipe systems to be based on the use of the building in addition to the height above or below for fire department access. According to the International Fire Code, Class III systems should be installed throughout the buildings where the level of the highest story is 30 feet higher than the lowest story. The code also requires the class I, II, III pipes in Group A buildings with more than 1000 people, in underground buildings, malls, boatyards, and marinas. Class I standpipes should be in every stairway for the floor above or below grade. They should be located in intermediate floor levels between floors and in exit passageways. Class III systems should conform to the requirements of Class I and II. However, the 130ft distance limitation does not apply in this case.
Fire Sprinkler Systems
Sprinkler systems come in four styles, including dry pipe, wet pipe, deluge, and pre-action. Wet pipe sprinkler systems are the most common and they have the fewest number of components hence take less installation time. The wet pipe system has a series of pipes that are connected to distributed fire sprinkler heads. The system cannot be connected in a place where the distribution pipes are exposed to low temperatures because they always have water. The operation of this system is dependent on heat reactive sprinkler heads (System Sensor, 2014). In case of a fire, the metallic heat sensor or fusible glass bulb in the sprinkler head shatters, melts, or separates. The action results in a discharge of water from the distribution pipe, which strikes the deflector and sprays water on the fire in a throw or any other engineered pattern. There are other variations of the wet pipe system, including one with an alarm check valve, with a straight pipe riser, and one with maintained excess pressure.
Dry pipe fire sprinkler systems are installed where the distribution pipes can be subjected to freezing temperatures like parking garages or unheated buildings. Unlike the wet pipe system which has water, this system has compressed air. The air is supplied by sources like nitrogen bottles or electric air compressors. The system has a valve clapper and alarm port. The valve clapper is closed by pressure differences between air and water pressure at its interface (System Sensor, 2014). To maintain this pressure, supervisory pressure switches are used and they can send a notification of low or high pressure to a panel. Upon receiving the notification, the panel can either release pressure using a ball valve or turn on a pump ensuring the right pressure is maintained. In case of a fire, the heat causes the sprinkler head to open releasing the compressed air. The dry valve opens and a force of water from the main line flows to the distribution pipes if the air pressure drops 10psi below normal. Once the water from the main line flows through the clapper valve, the alarm port senses the water exposure. A pressure switch then senses the increased pressure and sounds an alarm.
Deluge fire sprinkler systems are installed in places with high hazard operations like aircraft hangers, power generation stations, petrochemical plants and places with flammable liquids. The system works with an independent detection system that delivers water immediately to the area. It works similarly to the wet pipe system with an exception of incorporating open fire nozzles or sprinkler heads that do not operate alone. The water in this system is held back by an electric valve connected to a releasing panel. An initiating device sends a signal to a panel that energises the circuit to open the solenoid valve. In areas where this system is installed, water is not enough to control the fires and sometimes a foam concentrate is mixed through a part of the system called proportioner (System Sensor, 2014).
The foam is Aqueous Fire Fighting Foam, which when combined with water makes the concentrate expand to be released in the sprinkler head. Pre-action fire sprinkler systems are placed in water sensitive places like computer rooms. Such places require fire systems that will operate in an actual fire to save the building and its components. The system is like the dry pipe system, except they do not have to use air pressure. It is also similar to the deluge system but the valve is electronically closed and closed fire sprinklers are used. The valve opens only when an independent detection system in the same area is activated verifying the presence of a fire. When the valve opens, the system is turned to a standard wet system.
Fire Detection and Alarm Systems
The aim of this system is to identify the presence of a fire and to give an alert to the building occupants and fire emergency organisations in a timely way. Depending on the fire scenario, the type of the building and number of occupants, the system can be designed to provide main functions. A control panel is the main brain of the detection system. It is responsible for monitoring the input devices like the automatic detection components and activating output devices like alarms, warning lights and emergency phone dialers. The complexity of the control panel may vary from a simple unit with a single input and output point to a complex system that monitors several buildings.
Fire detectors are part of this system. Manual fire detection is where people are the detectors of fire. When a person does, they break the glass of a manual alarm station, which notifies other people. Thermal detectors are a type of automated detection device. Most common devices have a fixed temperature detecting device that is activated when the room reaches a predetermined temperature like between 57 to 74 degrees. Another form of thermal detector is the rate-of-rise detector that identifies an abnormal rise in temperature in a short period of time. The detectors are periodically placed on the building’s ceiling. Smoke detectors are designed to detect a fire while in its early stages. The most common detectors are placed on the ceilings. For open places like galleries, the detector used is a projected beam unit made up of a light transmitter and receiver. Such detectors are placed 300ft apart. In the presence of smoke, the light beam is obstructed and the receiver is unable to see a full beam. Such shows the presence of smoke and an alarm is activated. Upon the notification of fire, the control panel informs about the emergency. The output devices include horns, alarms, and warning lights.
Special Fire Protection Systems
The systems are used where there is equipment of high value or in areas with irreplaceable assets like in art galleries and museums.
Fire Extinguisher
It is a handheld device used to control small fires. It is designed for use in fires that are out of control, for instance, one that has spread to different rooms. Fire extinguishers are required to be inspected by a service company. Fire extinguishers are classified into different classes depending on their intended use. Class A is intended for basic solid substances like paper and plastic. Class B is intended for flammable liquids and gases while class C is for electrical equipment. Class D is for combustible metals. Class K is mostly used in kitchens for stopping oil and fat fires. The extinguishers are fitted in buildings at easy to access points like against the wall. Also, they can be found in motor vehicles, aircrafts, or boats. The common types of extinguishers are water, carbon dioxide, and dry chemical extinguishers. Water extinguishers are best for class A fires and are filled with water and then pressurised with air. Such extinguishers should not be used in other fires of a different class since they can worsen the situation (Fire Extinguisher 101, n.d.). Dry chemical extinguishers are appropriate for class A, B, and C fires. The extinguishers are filled with foam and pressurised with nitrogen. BC is the common type of dry chemical extinguisher and is filled with potassium bicarbonate or sodium bicarbonate. ABC is a multipurpose type of dry chemical extinguisher and is filled with monoammonium phosphate. Dry chemical extinguishers are said to have an advantage over carbon dioxide extinguishers. The dry chemical extinguishers leave a non-flammable substance on the material reducing the likelihood of more fire. The carbon dioxide extinguishers are used mostly for class B and C fires. The extinguisher does not work well with class A fires since the amount of oxygen may not be enough.
Smoke Control Systems
Smoke control systems are in buildings like prisons, hospitals, and malls. The system is intended to give the building’s occupants a habitable and safe environment for a period of almost 20 minutes. The systems are of two types; active and passive (Department of Insurance, 2010). Active smoke systems make use of a building’s fan system, duct, HVAC unit and more mechanical equipment with the intention of ventilating the smoke from the building and keeping it at a habitable level. Passive smoke systems make use of reservoirs and compartmentalisations to control the smoke to a predetermined level. The smoke systems are not designed to completely remove the smoke from the building.
References
Artim, N. (n.d.). Emergency Management: 3.2 An introduction to fire Detection, Alarm, and Automatic Fire Sprinklers. Northeast Document Conservation Center. Retrieved from https://www.nedcc.org/free-resources/preservation-leaflets/3.-emergency-management/3.2-an-introduction-to-fire-detection,-alarm,-and-automatic-fire-sprinklers
Fire Extinguisher 101. (n.d.). Fire Extinguisher Types. Retrieved from http://www.fire-extinguisher101.com/
Mettauer, D. (2007). Standpipe Systems Explained. Firewatch. Retrieved from https://c.ymcdn.com/sites/www.nafed.org/resource/resmgr/KnowledgeCenter/FW_2007Dec_Standpipes.pdf
System Sensor. (2014). Applications Guide: Fire Sprinkler Systems Monitoring. System Sensor. Retrieved from https://www.systemsensor.com/en-us/Documents/Sprinkler_AppGuide_WFAG557.pdf
