[Fire Safety] Nine common fire safety facilities

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bg2.png Fire-fighting facilities are a crucial guarantee for organizations to enhance their ability to resist fires. Maintaining them in good condition is essential for the timely detection of fires, effective control and extinguishment of fires, as well as providing assistance for evacuation and fire-fighting rescue operations. Through this section, you should become familiar with the basic concepts and working principles of common fire-fighting equipment, with a focus on mastering the usage methods and operational requirements for such equipment. 1 Fire doors and fire shutters: Fire doors and fire shutters are typically installed on fire walls; they possess good fire resistance, and in the event of a fire in a building, they help to contain the flames within certain limits. At the same time, it provides favorable conditions for the safe evacuation of people and fire fighting. (1) Fire doors: Fire doors refer to doors that, together with their frames, can meet the requirements for fire stability, integrity, and thermal insulation over a certain period of time. It is usually installed on the fire compartment partition walls, in evacuation stairwells, vertical shafts, and similar locations. 1. Composition of fire doors: Fire doors are composed of a door frame, a panel filled with insulating material, fire-resistant hardware fittings, electromagnetic door catches, and other components. The door leaves are connected via hinges; the door is equipped with a door closer and a fire lock. Double-door sets also come with hidden pins (installed on the fixed door leaf) and aligners to prevent the leaves from overlapping at the seam. Associated with the normally open fire doors are fire detectors and a fire linkage control system. 2. Classification of fire doors: By material – wooden fire doors, steel fire doors, steel-wooden fire doors, and fire doors made of other materials ； Classified by the number of door leaves: single-door fire door, double-door fire door, multi-door fire door ； Classified by structural type: fire doors with fire-resistant glass on the door leaf; fire door frames with single and double grooves; fire doors with vision panels; inorganic glass fire doors ； Classified by open/closed state: normally open fire doors, normally closed fire doors ； Classified by fire resistance: fire-resistant doors with insulation (Class A), partially insulated fire-resistant doors (Class B), and non-insulated fire-resistant doors (Class C). 3. Fire door control: Both normally open and normally closed fire doors open in the direction of evacuation. A release device and a single linkage module are installed on each single-door fire door, while two fire door release devices and two single linkage modules are installed on double-door fire doors. When a fire detector on either side of the fire door triggers an alarm, it reports this to the fire alarm controller via the bus. The fire alarm controller then sends an instruction to the fire door interlock module, which in turn activates the release mechanism to open the door. Once opened, the fire door closes automatically due to the elasticity of the door closer. At the same time, the fire door release device feeds the fire door status signal to the single-linkage module, which then sends it to the fire control room via the alarm bus. (II) Fire shutters: Fire shutters refer to shutters that, together with their frames, can meet the requirements for fire resistance integrity for a certain period of time. A fire curtain is a fire-resistant partition that operates by rolling vertically. Normally, it is rolled up and stored in a shaft box above door and window openings; during a fire, it is lowered and unfolded to prevent the spread of flames from those openings. Fire shutters are generally installed around escalators, at the openings connecting atriums with corridors on each floor, in lobbies and rooms, and in areas where fire separation measures are required as a substitute for firewalls. 1. Components of a fire-resistant rolling shutter: A fire-resistant rolling shutter is composed of curtain panels, base plates, guide rails, supports, reels, enclosures, control boxes, door operators, limiters, door lintels, manual release switch devices, push-button switches, and safety devices, among other components. Devices that are linked to fire dampers include smoke detectors, heat detectors, and a fire linkage control system. 2. Classification of fire shutters: Fire shutters can be classified according to their fire resistance rating into ordinary steel fire shutters (with a fire resistance rating of ≥2 hours), composite steel fire shutters (with a fire resistance rating of ≥3 hours), and premium-grade fire shutters (with a fire resistance rating of ≥4 hours). When ordinary steel fire shutters are used for fire separation, they need to be protected by an automatic sprinkler system. 3. Fire curtain control – Automatic control: Once a fire detector activates, the fire curtain, which serves as a fire barrier, descends to the bottom as part of the automated response ； Used as a fire curtain on evacuation routes; the curtain first descends to a height of 1.8 meters above the ground, and after another temperature sensor triggers, it descends all the way to the bottom. Mechanical operation: First, remove the chain and pull down the chain on the side of the rolling shutter, and the rolling shutter will descend ； Pull the chain on the other side downward, and the curtain will rise. Manual operation: Open the manual control box located on building components on or near both sides of the roller shutter. Press the “Up” button (or the button marked with the “Δ” symbol) to raise the roller shutter; press the “Down” button (or the button marked with the “” symbol) to lower it ； Press the middle button to stop the roller blind from moving ； The other method is: press the manual button corresponding to the control module that drives the roller shutter downward in the fire control room. When the shutter reaches the designated position, a feedback signal will be sent back to the fire control room. 2 Automatic Fire Alarm System The automatic fire alarm system is an automatic fire protection device installed in buildings or other locations, capable of detecting and reporting fires at an early stage. (1) System composition: An automatic fire alarm system typically consists of triggering devices such as fire detectors, alarm devices such as fire alarm controllers, warning devices such as audible and visual alarms, interlocking control devices such as bus control panels and control modules, as well as power supplies. (II) Working principle: In the early stages of a fire, the automatic fire alarm system converts physical parameters such as smoke, heat, and light radiation generated by the combustion into electrical signals using smoke detectors, heat detectors, and photoelectric detectors. These signals are transmitted to the fire alarm controller, where they are processed, analyzed, and evaluated. The results are then displayed in the form of sounds, lights, or text, along with indication of the location where the fire occurred, and the time of the fire is recorded as well. (III) Interlinked control: The automatic fire alarm system generally operates in conjunction with devices such as pre-action systems, deluge systems, water curtain systems, water spray systems, water cannon systems, gas fire suppression systems, smoke control and exhaust systems, ventilation systems, air conditioning systems, normally open fire doors, fire shutters, smoke barriers, and fire emergency broadcasting systems. In the event of a fire, when the controller is in automatic mode, it automatically activates smoke control fans, shuts down fresh air fans, closes fire dampers, and releases fire doors, fire shutters, and smoke barriers. It also automatically activates pre-action, deluge, water curtain, water spray, and water cannon pumps. Additionally, fire pumps and smoke control fans can be directly activated from the fire control room. 3 Smoke control system: The smoke control system is a building facility designed to control the flow of smoke within a building where a fire has broken out, to create conditions conducive to safe evacuation and firefighting efforts, and to prevent and reduce the hazards caused by building fires. Smoke control and exhaust systems are divided into mechanically pressurized air supply smoke control facilities and mechanical smoke exhaust facilities. (1) System composition: The main components of a smoke control system include smoke control fans, electrical control cabinets, air ducts, fire dampers, supply air outlets, exhaust air outlets, manual control devices, fire detectors, and fire linkage control systems. (II) Installation locations 1. Mechanical pressurized air supply smoke control systems These systems are mainly installed in: smoke control stairwells without natural smoke exhaust conditions, as well as in the front rooms of fire elevators or shared front rooms ； Smoke-proof stairwells equipped with natural smoke exhaust measures, as well as vestibules and enclosed refuge floors (rooms) that do not have conditions for natural smoke exhaust. 2. Mechanical smoke exhaust systems: Mechanical smoke exhaust systems are primarily installed in: interior corridors of buildings whose length exceeds 20.0 meters and where natural smoke exhaust is not possible; entertainment, dance, and gaming venues with a floor area exceeding 200 m²; as well as public buildings, Class C factories, and Class C warehouses whose areas exceed the specified limits. (III) Working principle: Smoke control and exhaust systems are generally linked to the fire alarm system. When the control panel in the control center is set to automatic mode, and a fire is detected, the smoke control and exhaust system is activated automatically. Mechanical pressure supply fans then start operating, delivering air under pressure to smoke-proof stairwells, the vestibules of fire elevators, or shared vestibules where natural smoke exhaust is not possible, thereby preventing smoke from entering ； At the same time, the fire dampers in the corresponding smoke prevention zones open automatically, and once the mechanical smoke exhaust fans start operating, the thick smoke is expelled outward through the exhaust openings into the smoke exhaust ducts or shafts. When the temperature reaches 280°C, the smoke exhaust fans stop working automatically. When it cannot start automatically, it can be started remotely from the fire control center, or the positive pressure supply fans and exhaust fans can be started directly at the fan room. 4 Outdoor fire hydrant water supply system: Outdoor fire hydrants are primarily used to supply water to fire trucks, or to connect directly to fire hoses and nozzles for extinguishing fires; they are essential fire-fighting water supply facilities in urban infrastructure. (1) System composition: The main components of outdoor fire hydrants include the body, elbow pipes, valve seats, valve discs, drain valves, valve stems, and fire connection fittings. They are divided into two types: above-ground type, whose upper part is exposed above the ground and is easily identifiable and convenient to use; and below-ground type, which is installed underground without affecting the appearance of the area. (II) Layout requirements: Outdoor fire hydrants should be installed along roads. When the road width is over 60 m, it is advisable to install them on both sides of the road, preferably near intersections. The spacing between them should not exceed 120 m; the distance from the road edge should not be more than 2 m. The distance from the exterior wall of a building should be no less than 5 m and no more than 150 m, while the distance from the exterior wall of a high-rise building should not exceed 40 m. The number of outdoor fire hydrants should be determined based on factors such as their coverage radius, flow rate, and the amount of water required for outdoor firefighting. The flow rate of each outdoor fire hydrant is estimated to be 10–15 L per second. Above-ground fire hydrants should be installed in a way that they are easily visible and accessible for use; fixed signs should be placed near the ground to indicate their location. (III) Method of use: The fire hydrant is usually closed, with the valve disc sealing the water inlet. When in use, connect the suction hose of the fire truck to the interface with a diameter of 100 mm (150 mm), or connect the hose to the interface with a diameter of 65 mm. Then, use a special wrench to open the valve, and the municipal water supply from the underground pipeline network will flow into the fire hydrant. The fire truck can then draw water directly for use, and the hose can also be used to deliver water for extinguishing fires. After use, close the valve; any remaining water inside the valve can be automatically drained through the drain valve. 5 Indoor fire hydrant water supply system. The indoor fire hydrant system is one of the main fire protection facilities in a building; fire hydrants serve as the primary tools for employees of an organization or firefighters to extinguish fires. (1) System components: The indoor fire hydrant system mainly consists of fire hydrant cabinets, indoor piping networks, fire water tanks, municipal inlet pipes, fire ponds, fire pump sets, hose connectors, fire pump control cabinets, test fire hydrants, etc. (II) Spacing requirements: In high-rise residential buildings, high-rise industrial buildings, elevated warehouses, and production facilities of categories A and B, the spacing between fire hydrants shall not exceed 30 m ； In other single-story and multi-story buildings, as well as in podiums directly attached to high-rise buildings, it should not exceed 50 m. (III) Method of use: Indoor fire hydrants are generally installed on the walls in public areas of buildings, with clear markings; they contain hoses and nozzles, and some also have fire reels. When using a fire reel, open the door of the fire hydrant box, pull out the hose, and turn on the switch of the small-diameter water gun to spray water and extinguish the fire ； When using a hose, open the door of the fire hydrant box, take out the hose and nozzle. Connect one end of the hose to the outlet of the fire hydrant and attach the nozzle to the other end; straighten the hose. Then press the button on the fire hydrant to start the pump, thereby activating the fire hydrant pump. Finally, open the valve of the fire hydrant to release water for extinguishing the fire. When the fire pump control cabinet is in manual mode, someone should be sent to the fire pump room to manually start the fire pump. 6 Automatic sprinkler systems. An automatic sprinkler system is a fixed, automatic fire-fighting facility that automatically detects fires and controls the release of extinguishing agents. Based on the operating mode of the sprinklers in the piping network, it can be classified into closed-system and open-system types. The closed-system automatic sprinkler systems include: wet-pipe systems, dry-pipe systems, pre-action systems, and re-circulating systems ； Open automatic sprinkler systems also include: deluge fire suppression systems, water curtain systems, and water spray systems. (1) Wet automatic sprinkler system: The wet automatic sprinkler system is so named because the piping network both before and after the alarm valve remains constantly filled with pressurized water. 1. System composition: It consists of closed-type sprinklers, piping systems, wet alarm valve assemblies, water flow indicators, fire water sources, and water supply facilities. 2. Working principle: Under the influence of the temperature in a fire scene, when the temperature-sensitive element of a closed-type sprinkler reaches the predetermined operating temperature, the sprinkler opens and starts spraying water to extinguish the fire. As the water flows within the piping system, the water pressure above the wet alarm valve decreases; the valve disc, which was previously in a closed state, opens due to this pressure difference. Water flows through the wet alarm valve into the main pipes and branch pipes. The flow indicator on the main pipes converts the flow signal of water into an electrical signal, which is then transmitted to the controller. The water in the branch pipes passes through a timer before reaching the hydraulic alarm bell and pressure switch. The flow of water causes the hydraulic alarm bell to produce a sound alarm signal, and at the same time it causes the contacts of the pressure switch to come into contact. This not only sends a contact signal back to the controller but also directly activates the sprinkler pump, ensuring that continuous pressurized water supply is provided to achieve the purpose of automatic fire suppression. After water is sprayed, the flow indicator and pressure switch send alerts to the alarm controller; information regarding the activation of the sprinkler pump is also fed back to the alarm controller. There are two ways in which a pressure switch can be powered: one is from the fire control panel, and the other is from the power control cabinet in the pump room. The pressure in the main sprinkler pipe is generally no more than 12 kg. If the pressure is too high, water should be supplied in zones. The pressure in branch pipes should generally not exceed 4–5 kg; if it does, pressure reduction is necessary. After the valve leading from the wet alarm valve to the delay device opens, the sprinkler pump starts immediately; the main reason is that the valve disc does not close tightly. The spray pump is fault-free, but it still won’t start after the end outlet is opened? The main reason is that the gauge pressure below the wet alarm valve is too low (there is no pressure stabilization or the pipes connected to the roof water tank are not functional), preventing the pressure switch from making contact; moreover, the hole beneath the timer has widened. After the end discharge valve is closed, why can’t the spray pump stop? Mainly because the pressure switch cannot disengage automatically. The pump still had not started 90 seconds after water was released at the end; the main reasons were: the pressure gauge below the wet alarm valve showed too low a pressure (there was no pressure stabilization or the pipes connected to the rooftop water tank were not functional), the pressure switch could not make contact, the hole beneath the timer had widened, the sprinkler control panel was not set to automatic mode, and the power supply to the pump was turned off. (II) Dry pipe sprinkler systems. Dry pipe sprinkler systems were developed based on wet pipe systems to meet the need for installing automatic sprinkler systems in cold and high-temperature environments. Since there is no water in its pipes and nozzles at normal times, and they are in a pressurized state, it is called a dry system or a dry-pipe system. 1. System composition: It consists of closed-type nozzles, piping systems, dry alarm valve assemblies, water flow indicators, inflation equipment, exhaust equipment, fire water sources, and water supply equipment. 2. Working principle: In the event of a fire, the temperature of the temperature-sensitive element in the closed-type nozzle rises due to the high temperature at the fire site. When this temperature reaches the predetermined operating range, the nozzle opens, and the compressed air in the pipeline is released from the nozzle, causing the pressure on the outlet side of the dry alarm valve to drop. As a result, the dry alarm valve opens automatically, allowing water to enter the pipeline and be discharged through the nozzles. When the dry-type alarm valve is opened, the path to the hydraulic alarm bell is also opened; water flow strikes the hydraulic alarm bell to generate an audible alarm signal. The pressure switch’s alarm signal is sent to the alarm controller, which in turn activates the fire pump to supply pressurized water. (III) Pre-action sprinkler fire suppression system: The pre-action sprinkler fire suppression system is a fire suppression system that integrates wet pipe systems, dry pipe systems, and fire alarm systems. In this system, the piping network downstream of the valve remains dry, while the piping network upstream of the valve remains wet. In the event of a fire, the automatic fire alarm system controls the pre-action valve, causing the piping network downstream of the valve to be filled with water immediately, thereby converting the system into a wet pipe system. Hence, it is called a pre-action sprinkler fire suppression system. 1. System composition: It consists of fire detectors, alarm control devices, closed-type sprinklers, piping systems, pre-action valve assemblies (or deluge valve assemblies), manually operated valves, inflation equipment, exhaust devices, fire water sources, and water supply facilities. 2. Working principle: The pipeline network behind the valves in this system is generally filled with low-pressure compressed air. In the event of a fire, the fire detectors installed in the protected area first send out an alarm signal. Upon receiving this signal, the fire control panel automatically opens the exhaust valve to release air, and it also automatically opens the solenoid valve to allow water to flow in. The valve discs, which were previously in a closed state, open due to the pressure difference, allowing pressurized water to quickly fill the pipeline network. As a result, the system, which was originally of the dry type, rapidly transforms into a wet-type system; subsequent operations then proceed in the same manner as those of a wet-type system. (IV) Deluge sprinkler systems: When a deluge sprinkler system is activated, all sprinklers discharge water simultaneously, creating a downpour-like effect; hence it is also known as a deluge system or flood system. 1. System composition: It consists of a fire detection and alarm control device, open-type sprinklers, piping systems, deluge valve assemblies, manually operable valves, fire water sources, and water supply facilities. 2. Working principle: In the event of a fire, the fire detector sends a signal to the fire alarm controller, which then sends a signal to activate the deluge valve, allowing the open-type sprinklers throughout the protected area to release water to extinguish the fire. The water pump is started simultaneously to ensure a supply of water, with the pressure switch and hydraulic alarm activating together. When no water is sprayed after the automatic alarm is activated, the solenoid valve should be manually opened. (5) Water spray fire extinguishing system: The water spray fire extinguishing system is commonly used to protect storage tanks for flammable liquids and gases, as well as oil-immersed power transformers. The composition and working principle of the water spray fire suppression system are basically the same as those of the deluge system. The main difference lies in the structure and performance of the nozzles: wet pipe systems use standard open-type nozzles, while water spray systems employ medium- or high-speed spray nozzles. Pre-action systems, deluge fire suppression systems, water spray fire suppression systems, and automatically controlled water curtain systems shall open the solenoid valves immediately upon an alarm from the fire alarm system, to supply water automatically to the distribution pipes. They shall also provide three ways of starting the water pump: automatic control, manual remote control from the fire control room, and on-site emergency operation. 7 Foam fire extinguishing system: Foam is one of the most effective extinguishing agents for Class B fires. It features safety and reliability, cost-effectiveness, and high fire suppression efficiency. (1) System composition: A foam fire extinguishing system consists of a fire water source, fire pump sets, a foam concentrate supply source, a foam proportioning mixer, pipelines, and foam generating devices. (II) System classification: Foam fire extinguishing systems are classified into three types based on their method of installation and use: fixed, semi-fixed, and mobile ； Based on the spraying position of the foam, it is divided into surface spraying and submersed spraying ； Based on the foam expansion ratio, it can be further divided into three types: low expansion, medium expansion, and high expansion. (III) Working principle: During the discharge of water from the fire suppression pipeline, a proportioning mixer is used to mix foam liquid with water in the right proportions to form a foam mixture. This foam mixture passes through a foam generator, where it mixes with the air drawn in, resulting in the formation of foam. The foam is then sprayed onto the surface of the burning liquid, creating a foam layer that isolates air and absorbs heat, thereby extinguishing the fire. Foam extinguishers are primarily used to fight Class B fires, and they can also be used to extinguish Class A fires. (IV) Usage Method 1. Above-surface fixed foam fire extinguishing system: In the event of a fire in an oil tank, the duty personnel must first start the fire pump to fill the fire suppression network with water. At the same time, it is necessary to open the valves for foam and cooling systems on the tank involved in the fire, as well as the valves of the cooling networks of adjacent tanks. It is also important to check whether the valves in the foam liquid storage tank are open, whether the output ratio is normal, and whether there is sufficient amount of foam liquid available. Upon arrival at the scene, the commander first checks whether the fire pump has started and whether the foam output is normal. If it is found that the fire pump has not started or the foam output is abnormal, personnel should be sent immediately to start it and conduct an inspection. 2. Semi-fixed foam fire extinguishing system above the liquid level: In this system, the foam generator is fixedly installed on the oil tank, while the pipeline section below is placed outside the tank’s protective dike; the pipeline extends outside the dike at a height of 1 meter above the ground, with a connection fitting at its end, which is normally covered by a lid. The foam mixture is supplied by a mobile foam fire truck. In the event of a fire, a foam fire truck arrives at the scene. The firefighters connect the hose connections outside the protective barrier, adjust the proportioning mixer to raise the pressure at the outlet of the truck’s fire pump to the normal operating pressure, and then open the ball valve at the truck’s outlet to supply the foam mixture to the semi-fixed system. Air is drawn in through the generator to produce foam. 3. Mobile foam fire extinguishing system: A mobile foam system is generally used when there is no fixed fire extinguishing system installed in the oil tank, or when the top of the oil tank is damaged as a result of a fire, or when the fixed fire extinguishing system is destroyed. Mobile fire extinguishing systems primarily utilize foam fire trucks, which use on-board foam nozzles to spray foam directly at oil tanks in order to extinguish the fire. Alternatively, fire trucks are used; by adjusting the operating pressure (including the ratio of the foam mixture), the mixture is delivered through fire hoses to mobile foam nozzles, foam guns, and foam hoses, thereby generating foam for fire suppression. To extinguish running fires, foam can be sprayed using a foam truck with a foam gun, or a foam hydrant with a hose gun. 8 Gas fire extinguishing system: The gas fire extinguishing system is used in specific locations. Since it leaves no traces after extinguishing a fire and does not affect the normal operation of equipment, it is an ideal automatic fire extinguishing system. (1) System composition: A gas fire extinguishing system consists of storage devices (start-up cylinders, fire-extinguishing cylinders), start-up and distribution devices, pipelines, delivery and release devices, fire detectors, fire control panels, monitoring devices, and other components. (II) System classification: Gas fire suppression systems are classified according to the extinguishing agents used, including carbon dioxide fire suppression systems, halon replacement fire suppression systems, Novec fire suppression systems, and aerosol fire suppression systems ； Classified by fire extinguishing method: total flooding gas fire extinguishing system, local application gas fire extinguishing system ； Based on the layout of the piping network, they are divided into pipeline-based fire suppression systems and pipeline-free fire suppression systems. (III) Working Principle: The working principle of a gas fire extinguishing system is as follows: Upon receiving a fire alarm signal, the fire control center activates the associated devices (closing openings, shutting down air conditioning, activating alarms, etc.). After a delay of about 30 seconds, the solenoid valve of the starting gas cylinder is opened; the high-pressure nitrogen in this cylinder is used to open the valve of the fire extinguishing gas cylinder. The fire extinguishing agent is then delivered through pipes to the nozzles, from where it is released to extinguish the fire. The delay in the middle is taken into account to allow for the evacuation of people within the protected area. (IV) System control: To ensure that the system starts in a timely and reliable manner in the event of a fire, its control and operation must meet certain requirements. Piped gas fire extinguishing systems should generally have three modes of activation: automatic control, manual control, and mechanical emergency operation ； A pipeless fire extinguishing system should have two modes of activation: automatic control and manual control ； When a locally applied gas fire extinguishing system is used in protected areas where people are often present, automatic control may not be required. 9 Fire Control Room: The fire control room serves as the information control center for a building’s fire protection systems, as well as the command center for firefighting operations during a fire. It holds a very important position and plays a crucial role. (1) Location of the control room: The fire control room should be located on the ground floor of the building. A sign or indicator light should be placed above the door to the fire control room. In the case of a fire control room located on the basement floor, the sign on its door must be a device equipped with a light cover. The power supply for the indicator lights should be connected to the fire protection power supply to ensure a reliable power supply for them. To prevent fires from threatening the safety of the personnel in the fire control room, its doors must have a certain level of fire resistance (that is, they should be Class A fire-resistant doors), and they should open in the direction of evacuation, with safe exits available. (II) Functions of control equipment: Fire control equipment is capable of starting and stopping fire pumps, as well as smoke prevention and exhaust fans. In addition to automatic control, it also allows for direct manual control. In the event of a fire, it automatically shuts down normally open fire doors, fire shutters, and electric fire valves; it stops air supply to relevant areas, brings elevators to a stop, cuts off non-fire-related power supplies in those areas, activates alarm devices, emergency lighting, and evacuation sign lights, starts emergency broadcasts, and receives feedback signals from them. It also has control and display functions for gas fire extinguishing systems and foam fire extinguishing systems. (III) Requirements for communication equipment: Special fire phones shall be installed in the fire control room and duty rooms, fire pump rooms, generator rooms, power distribution rooms, ventilation and air conditioning rooms, smoke exhaust rooms, elevator rooms, as well as other rooms related to fire linkage control where personnel are stationed on a regular basis; at the operating units of the fire extinguishing control system or in the control rooms; and in enterprise fire stations, fire duty rooms, main dispatch rooms, etc ； A intercom phone jack is provided at the manual alarm button ； Places such as fire control rooms, fire duty rooms, or corporate fire stations are equipped with external telephones for direct alarm reporting.