Fire detection and alarm systems

FireFire detection and Alarm system

SUBMITTED TO:

SUBMITTED BY:

AR. KIRANPREET KAUR

PRAGYAA VASHISHTHASURAJ VEER SINGHTRISHANJIT SINGH

FIRE• Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition

• Fire in its most common form can result in conflagration, which has the potential to cause physical damage through burning. Fire is an important process that affects ecological systems around the globe. The positive effects of fire include stimulating growth and maintaining various ecological systems.

HOW DOES FIRE SPREAD?ONCE STARTED, A BUILDING FIRE IS LIKELY TO SPREAD UNTIL ALL FUEL HAS BEEN USED UP. THIS COULD HAVE DEVASTATING CONSEQUENCES FOR YOUR HOME OR BUSINESS. BY UNDERSTANDING HOW FIRE SPREADS, YOU MAY BE BETTER EQUIPPED TO EXTINGUISH IT.• CHEMICALS AND COMBUSTIBLES: WHEN FIRE COMES IN CONTACT

WITH LAB CHEMICALS, HOUSEHOLD CLEANERS, PAINT AND OTHER CHEMICALS, THE FIRE BURNS HOTTER AND MORE AGGRESSIVELY, ENCOURAGING IT TO SPREAD. OTHER COMBUSTIBLES COMMONLY FOUND IN THE HOME INCLUDE MATTRESSES, SOFA CUSHIONS, MAGAZINES, NEWSPAPERS AND VARIOUS TEXTILES.

• OPEN SPACE: A BUILDING WITH LIMITED INTERIOR STRUCTURE BURNS MUCH FASTER THAN ONE WITH HALLWAYS AND CLOSED DOORS. WALLS AND DOORS TRAP THE FIRE AND PREVENT THE FLAMES AND SMOKE FROM SPREADING. WHILE THE FIRE WILL EVENTUALLY BURN THROUGH THE STRUCTURE AND CONTINUE TO SPREAD IF LEFT TO ITS OWN DEVICES, A FIRE FIGHTING TEAM HAS A MUCH EASIER TIME DOUSING THE FLAMES IN A BUILDING WITH MORE WALLS AND DOORS, ESPECIALLY IF THOSE STRUCTURES ARE BUILT TO WITHSTAND THE HEAT AND DAMAGE OF A FIRE.

• Construction materials: While a fire can burn through just about any modern building, fire resistive buildings made of concrete and steel curb the spread of fire better than wood frame homes.• Water: In some cases, water is not the best fire extinguisher. Grease fires, for example, can actually spread faster when doused with water. A special fire extinguisher or baking soda should be used to suffocate and stop the spread of grease fires in the kitchen.

CAUSES OF FIREKitchen Stoves:

• Never leave the stove unattended.

• Check that electric cords, curtains, tea towels and oven cloths are at a safe distance from the stove top.

• Be careful of long flowing sleeves contacting gas flames.

Electric Blankets:

• Do not sleep with electric blankets on or leave the house without switching them off.

• Never leave weighty objects on the bed when the electric blanket is on.

• Have your blanket checked by an authorised repairer if you suspect overheating.

• Always follow manufacturer´s instructions for care and storage.

• Inspect each blanket for wear and tear at the beginning of the cooler months.

Faulty Wiring: • Always use a qualified electrician.• Double adaptors and power-boards can overload power points.• Install safety switches and correct fuses.Smoking in Bed: • Smoking in bed can be fatal - tiny embers can smoulder unnoticed and

burst into flame much later.Lighting: • Check light fittings for heat build up.• Discard lampshades that are close to light globes & lamp bases that can be

knocked over easily.• Ensure recessed downlights are properly insulated from wood panelling or

ceiling timbers.Flammable Liquids: • Store all flammable liquids such as petrol, kerosene, methylated spirits

away from heat.• Always check the label before use and storage.• Use extreme care when pouring.

Clothes Dryers: • Always clean lint filters after each load.• Avoid drying bras in your dryer as the underwire can get caught and

start a fire.Candles: • Never leave burning candles unattended. Do not sleep with a burning

candle.• Make sure curtains and other flammable items are well away from

burning candles.Home Heating: • Make sure all appliances are professionally installed.• Check that walls and floors are insulated from heat sources.• Be careful where you place portable appliances.• Place a mesh guard in front of open fires.Children: • Warn all children about playing with fire.• Keep all matches, lighters and candles out of reach of small children.• Teach young children to bring matches or lighters they find to an adult

immediately.• Teach older children that matches are a tool to be used in the presence

of adults.

FireDetection

Detection • Fire detectors sense one or more of the products or phenomena resulting from fire, such as smoke heat, infrared and/or ultraviolet light radiation, or gas.

• In dwellings, smoke detectors are often stand-alone devices. In non-domestic buildings, fire detection will typically take the form of a fire alarm system, incorporating one or more of the following automatic devices

Fire

Devices

• Heat detector

• Smoke detector

• Flame detector

• Fire gas detector

Heat detector• A 'heat detector is a fire alarm device designed to respond when the convicted thermal energy of a fire increases the temperature of a heat sensitive element. The thermal mass and conductivity of the element regulate the rate flow of heat into the element. • All heat detectors have this thermal lag. Heat detectors have two main classifications of operation, "rate-of-rise" and "fixed temperature." The Heat detector is used to help in the reduction of damaged property. It is triggered when temperature increases.

Fixed temperature heat detectors

• This is the most common type of heat detector. Fixed temperature detectors operate when the heat sensitive eutectic alloy reaches the eutectic point changing state from a solid to a liquid. • Thermal lag delays the accumulation of heat at the sensitive

element so that a fixed-temperature device will reach its operating temperature sometime after the surrounding air temperature exceeds that temperature. • The most common fixed temperature point for electrically

connected heat detectors is 136°F (58°C). Technological developments have enabled the perfection of detectors that activate at a temperature of 117°F (47°C), increasing the available reaction time and margin of safety.

Rate-of-rise heat detectors

• Rate-of-Rise (ROR) heat detectors operate on a rapid rise in element temperature of 12° to 15°F (6.7° to 8.3°C) increase per minute, irrespective of the starting temperature. This type of heat detector can operate at a lower temperature fire condition than would be possible if the threshold were fixed. • It has two heat-sensitive thermocouples or thermistors. One

thermocouple monitors heat transferred by convection or radiation. The other responds to ambient temperature. Detector responds when first’s temperature increases relative to the other.• Rate of rise detectors may not respond to low energy release rates of

slowly developing fires. To detect slowly developing fires combination detectors add a fixed temperature element that will ultimately respond when the fixed temperature element reaches the design threshold.

Rate of rise detector

Fixed temperature detector

Smoke detector

• A smoke detector is a device that senses smoke, typically as an indicator of fire. Commercial security devices issue a signal to a fire alarm control panel as part of a fire alarm system, while household smoke detectors, also known as smoke alarms, generally issue a local audible or visual alarm from the detector itself.

Working of smoke detector

Types of smoke detectors

• Ionization smoke detector

• Photoelectric, or optical, smoke detector

• Carbon monoxide and carbon dioxide detection

Ionization smoke detector• An ionization smoke detector uses a radioisotope, typically

americium-241, to ionize air; a difference due to smoke is detected and an alarm is generated. Ionization detectors are more sensitive to the flaming stage of fires than optical detectors, while optical detectors are more sensitive to fires in the early smoldering stage.

Photoelectric, or optical, smoke detector

• A photoelectric, or optical, smoke detector contains a source of infrared, visible, or ultraviolet light (typically an incandescent light bulb or light-emitting diode), a lens, and a photoelectric receiver (typically a photodiode). • In spot-type detectors all of these components are arranged

inside a chamber where air, which may contain smoke from a nearby fire, flows. • In large open areas such as atria and auditoriums,

optical beam or projected-beam smoke detectors are used instead of a chamber within the unit: a wall-mounted unit emits a beam of infrared or ultraviolet light which is either received and processed by a separate device, or reflected back to the receiver by a reflector

• In some types, particularly optical beam types, the light emitted by the light source passes through the air being tested and reaches the photo sensor. • The received light intensity will be reduced by absorption due to smoke, air-borne dust, or other substances; the circuitry detects the light intensity and generates the alarm if it is below a specified threshold, potentially due to smoke.

• In other types, typically chamber types, the light is not directed at the sensor, which is not illuminated in the absence of particles. • If the air in the chamber contains particles (smoke or dust), the light is scattered and some of it reaches the sensor, triggering the alarm.

1: Optical chamber2: Cover3: Case moulding4: Photodiode (detector)5: Infrared LED

Carbon monoxide and carbon dioxide detection

• Carbon monoxide sensors detect potentially fatal concentrations of carbon monoxide gas, which may build up due to faulty ventilation where there are combustion appliances such as heaters and cookers, although there is no uncontrolled fire outwith the appliance.

• High levels of carbon dioxide (CO2) may indicate a fire, and can be detected by a carbon dioxide sensor. Such sensors are often used to measure levels of CO2 which may be undesirable but not indicative of a fire; this type of sensor can also be used to detect and warn of the much higher levels generated by a fire.

Flame detector

• A flame detector is a sensor designed to detect and respond to the presence of a flame or fire. Responses to a detected flame depend on the installation, but can include sounding an alarm, deactivating a fuel line (such as a propane or a natural gas line), and activating a fire suppression system. • When used in applications such as industrial furnaces, their role is to

provide confirmation that the furnace is properly lit; in these cases they take no direct action beyond notifying the operator or control system. • A flame detector can often respond faster and more accurately than

a smoke or heat detector due to the mechanisms it uses to detect the flame.

Fire Gas Detector

• This detector is mostly used in factories where gas can cause fire and can be dangerous and lethal

• This type of detector is generally placed on the pipes in factories to prevent any kind of leakage.

Fire Gas Detector

Fire alarm system

Fire alarm system• A fire alarm system is number of devices working together to

detect and warn people through visual and audio appliances when smoke, fire, carbon monoxide or other emergencies are present. • These alarms may be activated from smoke detectors, and heat

detectors. Alarms can be either motorized bells or wall mountable sounders or horns. • They can also be speaker strobes which sound an alarm, followed by

a voice evacuation message which warn people inside the building not to use the elevators. They may also be activated via manual fire alarm activation devices such as manual call points or pull stations. • Fire alarm sounders can be set to certain frequencies and different

tones including low, medium and high, depending on the country and manufacturer of the device.

Parts•Fire alarm control panel (FACP) AKA fire alarm control unit (FACU); This component, the hub of the system, monitors inputs and system integrity, controls outputs and relays information.

•Primary power supply: Commonly the non-switched 120 or 240 volt alternating current source supplied from a commercial power utility. In non-residential applications, a branch circuit is dedicated to the fire alarm system and its constituents. "Dedicated branch circuits" should not be confused with "Individual branch circuits" which supply energy to a single appliance. •Secondary (backup) power supplies: This component, commonly consisting of sealed lead-acid storage batteries or other emergency sources including generators, is used to supply energy in the event of a primary power failure.

• Initiating devices: This component acts as an input to the fire alarm control unit and are either manually or automatically activated. Examples would be devices pull stations, heat detectors, or smoke detectors. Heat and smoke detectors have different categories of both kinds. Some categories are beam, photoelectrical, aspiration, and duct.• Notification appliances: This component uses energy supplied

from the fire alarm system or other stored energy source, to inform the proximate persons of the need to take action, usually to evacuate. This is done by means of a flashing light, strobe light, electromechanical horn, "beeper horn", chime, bell, speaker, or a combination of these devices. The System Sensor Spectralert Advance Horn makes a beeping sound and electromechanical sound together. Strobes are either made of a xenon tube (most common), or now LED lights.• Building safety interfaces: This interface allows the fire alarm

system to control aspects of the built environment and to prepare the building for fire, and to control the spread of smoke fumes and fire by influencing air movement, lighting, process control, human transport and exit.

Initiating Devices

• Manually actuated devices; also known as fire alarm boxes, manual pull stations, or simply pull stations, break glass stations, call points or buttons. Devices for manual fire alarm activation are installed to be readily located (near the exits), identified, and operated.• Automatically actuated devices can take many forms intended to

respond to any number of detectable physical changes associated with fire: convected thermal energy; heat detector, products of combustion; smoke detector, radiant energy; flame detector, combustion gasses; fire gas detector, and release of extinguishing agents; water-flow detector

Initiating Devices

Notification Appliances• Notification Appliances utilize audible, visible, tactile, textual or

even olfactory stimuli (odorizer)to alert the occupants of the need to evacuate or take action in the event of fire or other emergency. • Evacuation signals may consist of simple appliances that transmit

encoded information, coded appliances that transmit a predetermined pattern, and or appliances that transmit audible and visible textual information such as live or pre-recorded instructions, and illuminated message displays.• Fire alarm evacuation signals generally consist of a standardized

audible tone, with visual notification in all public and common use areas. Emergency signals are intended to be distinct and understandable to avoid confusion with other signals.

Notification Appliances

Emergency voice alarm communication systems

• Some fire alarm systems utilize emergency voice alarm communication systems (EVACS) to provide pre-recorded and manual voice messages. Voice Alarm systems are typically used in high-rise buildings, arenas and other large "defend-in-place" occupancies such as Hospitals and Detention facilities where total evacuation is difficult to achieve.• Voice-based systems provide response personnel with the ability to

conduct orderly evacuation and notify building occupants of changing event circumstances.• In high rise buildings, different evacuation messages may be played

to each floor, depending on the location of the fire. The floor the fire is on along with ones above it may be told to evacuate while floors much lower may simply be asked to stand by.

Emergency voice alarm communication systems

Mass notification systems/emergency communication systems

• Mass notification systems often extend the notification appliances of a standard fire alarm system to include PC based workstations, text based digital signage, and a variety of remote notification options including email, text message, RSS feed, or IVR based telephone text-to-speech messaging.

Mass notification systems/emergency communication systems

Building safety interfaces

• Magnetic smoke door holders

• Duct mounted smoke detection

• Emergency elevator service

• Public address rack (PAR)