Fire Safety Systems Flashcards
Fire Safety Systems:
The functions of fire alarms and sprinkler systems are
To detect a fire at and early stage.
To sound a building occupant warning or alarm system.
To transmit a signal to summon the fire system.
To interface with other fire safety subsystems.
To commence extinguishment of the fire.
Fire Safety Systems:
The three types of dry alarms are
Heat detectors
Smoke detectors
Flame detectors
Fire Safety Systems:
Info about heat detectors
Used in applications where smoke detectors are not suitable such as in non-life safety installations where the environment has too many airborne particles due to excessive steam, moisture, dust, humidity or temperature, such as in attics, garages, warehouses, storage facilities, elevator machine rooms or electrical closets.
Heat detectors can operate via fixed temperature or rate of rise.
Fire Safety Systems:
Where would you find heat probes
Heat probe detectors are mostly found in kitchen exhaust hood or areas where the ambient temperature is excessively high. Their operating temperature varies and can be calibrated to range from 60-270 degrees.
Fire Safety Systems:
4 main groups of smoke detectors
Smoke detection as opposed to heat detection is specifically designed for the protection of life by its ability to detect fire in its early stages.
the 4 main groups are:
Point type
Beam type
Sampling type (e.g. VESDA Very Early Smoke Detection Apparatus)
Residential smoke alarms
Fire Safety Systems:
Point type smoke detectors
Detect smoke at a single point or location.
There is two main group of which they work:
Ionisation or Photo-electric
Fire Safety Systems:
Beam type smoke detectors
Made up of a transmitter and a receiver located on opposite walls of the building or room being protected. usually found in open areas such as atriums, convention centres and warehouses.
Beam detector relies on the breaking, by smoke, of a long light beam.
Fire Safety Systems:
Sampling type smoke detectors
The air sampling system draws air from the protected area through tiny holes in a pipe work system spaced out uniformly around the room. Pipes are connected to detector control unit where there is a fan that creates flow inside. The flow creates a slight vacuum which allows air to be drawn in. A dust filter reduces the chance on contamination. The air is then sampled at a central point by a sensitive light scattering detector.
Can be used in large areas and is very sensitive.
Fire Safety Systems:
Residential smoke detector/alarm
Used in residential housing, work on ionisation or photo-electric.
Are stand alone detector and alarm systems.
Powered by either battery or mains power.
New homes are required to have Smoke detectors connected to mains power.
Fire Safety Systems:
Main groups of flame detectors
Flame detectors are radiation detectors and belong to two groups:
Infra-red (IR)
Ultra-violet (UV)
Used in the following situations:
Flammable liquid storage
Fuel or lubrication systems
Aircraft hangers
Fire Safety Systems:
Sprinkler systems will be required in
Buildings over 25m.
Enclosed carparks accommodating more than 40 vehicles.
Occupancies of excess hazard, e.g. tyre storage facilities, factories.
Shopping centres over 3500m2.
Certain large isolated buildings.
Buildings with atriums installed.
Fire Safety Systems:
The basic functions of a sprinkler system are
Detect the presence of fire.
Locate the area involved in fire.
Raise the alarm, both with the occupants of the building and the fire brigade.
Attack the fire.
Fire Safety Systems:
Sprinkler system design classification
Sprinkler design and installation has been divided into three main hazard classifications: Light hazard (LH) Ordinary hazard (OH) High hazard (HH)
Fire Safety Systems:
Sprinkler system light hazard classification
Light hazard (LH) occupancies are non industrial premises where the amount and combustibility of the contents is low, e.g. Art galleries, churches, offices, etc.
Fire Safety Systems:
Sprinkler system ordinary hazard classification
Ordinary hazard (OH) occupancies are commercial and industrial occupancies involving the handling, processing and storage of mainly ordinary combustible materials unlikely to develop intensely burning fires in the initial stages. Further subdivided into 4 groups (OH1-4). Examples are footwear manufacturing, motor garages, and paper mills/storage.
Fire Safety Systems:
Sprinkler system high hazard classification
High hazard (HH) occupancies are commercial and industrial occupancies with high fuel loads. Has two broad components: Process risk - where the materials handled are mainly of an extra hazardous nature likely to develop rapid and intensely burning fires, e.g. aircraft hangers, flammable liquid spraying. High piled risk - where goods are stacked above acceptable limits for fire protection by ordinary hazard sprinkler systems, e.g. tyre storage, wooden pallet storage.
Fire Safety Systems:
9 Types of sprinkler systems
Wet pipe
Dry pipe
Pre-action
Tail-end
Alternate wet and dry
Drencher
Deluge system
Floor by floor
ESFR (Early Suppression Fast Response)
Fire Safety Systems:
Wet pipe sprinkler systems
System pressurised with water. Is activated when sprinkler head in fractured either accidently or from the heat from a fire.
As water is used, pressure in the system drops. When its below or equal to town mains the alarm valve will lift and allow continuous water to flow.
Water will activate a local alarm bell and activate the pressure switch, the latter causing an automatic F&R notification and interface with other fire safety systems.
Water will continue to flow until main wheel valve is shut.
Can be installed where ambient temperature is consistently above 4 and below 70 degrees.
Fire Safety Systems:
Dry pipe sprinkler systems
Dry pipe systems don’t contain water. Instead they’re pressurised by air or nitrogen.
Found in areas of extreme cold where there is danger of water freezing or temperatures above 70 degrees.
Operate the same as wet systems, once air flows out and pressure drop alarm allows water to flow through.
Fire Safety Systems:
Pre-action sprinkler systems
A dry pipe systems that consists of both heat or smoke detectors and sprinkler heads.
When the detector activated it allows water to fill the pipe system. The when the sprinkler head activates it allows water to flow out.
Gives greater security from accidental release of water.
Fire Safety Systems:
Tail-end sprinkler system
Similar to other systems except it only forms an extension to the sprinkler system.
Fire Safety Systems:
Floor by floor combined system system
Floor by floor systems consist of sprinkler and hydrant combined systems serving one floor at a time.
In most cases may not have a sprinkler control room but can be isolated in the fire isolated stairwell.
Each floor has its own sprinkler valve set.
Fire Safety Systems:
Drencher systems
Can be their own system or an extension of the eternal sprinkler system. Can be operated manually or automatically.
Designed to provide discharge of water over the external openings of the building to prevent the spread of fire to nearby buildings.
Can be wall or curtain drenchers or window drenchers.
Fire Safety Systems:
Deluge systems
A system of open sprinklers controlled by a quick-opening valve (deluge valve) which is operated by a system of smoke/heat detectors, sprinklers in the same area as the open sprinklers. Deluge systems can be operated manually.
Deluge systems are dry pipe systems where all the water discharges simultaneously from all sprinkler heads in the zone. Deluge systems are typically used where very rapid fires can develop, e.g. aircraft hangers, flammable liquid stores.
