Fire Alarm Flashcards
What are the four methods of extinguishing a fire?
Starvation, Cooling, Smothering, Interference
What is starvation?
Depriving the fire of fuel (combustible materials)
What is cooling?
Depriving the fire of heat (applying water)
What is smothering?
Depriving the fire of oxygen
What is interference?
Applying extinguishing agents such as dry chemical
What is a pool fire?
A pool of liquid on a flat surface that is ignited
What is the average time for flashover to occur?
3-5 minutes
What is flashover?
When the heat at the top of the room meets the heat at the bottom of the room, the difference in temp causes an almost instantaneous combustion.
During fire spread, what catches on fire, the fuel or the vapour?
The vapors. Fire can be spread to different materials and objects without direct contact with a flame because the carbon gases ignite
What are the three types of ‘common’ fires?
Ordinary combustibles, flammable liquids, electrical fires
What are the two types of ‘specialty’ fires?
Combustible metals, kitchen/cooking oils
What is a class A fire?
Ordinary combustibles.
- wood, paper, cloth
- Picture is garbage can or wood burning
What is a class B fire?
Flammable liquids.
- For use on gas or oil in a barrel
- Picture is a gas can
What is a class C fire?
Energized electrical equipment.
- C for Current
- Picture is an electrical cord
What is a class D fire?
Combustible metals
- magnesium, potassium, titanium
- Picture is an I beam
What is a class K fire?
Kitchen fires
- cooking oils, fats, or grease
- Picture is a pan on fire
What happens if you use the wrong class of extinguisher on a fire?
Causes exothermic reaction
What is an exothermic reaction?
A chemical reaction that occurs in the form of light or heat.
Ex) adding water to an oil fire causes water to heat extremely fast to the point of steam, steam combusts with oil and causes an explosion
What does PASS stand for?
Pull, aim, squeeze, sweep
What are dry chemicals good for extinguishing?
Chemical reactions between heat and fuel
- Class A, B, and C
What are foam extinguisher agents good for?
Removes oxygen from the equation, good for preventing flashover
- Class A, B, and K
What is the only class that water should be used to extinguish?
Class A, combustible materials
What is the only extinguishing agent allowed for Class D fires?
Class D powder (M28 and L2)
What are wet chemical extinguishing agents used for?
Class A, and Class K fires
What are carbon dioxide extinguishing agents used for?
Class B and class C
What are the only two types of approved extinguishing agents for Class C fires?
Dry chemical and carbon dioxide
What is the main advantage of carbon dioxide extinguishing agents?
Removes heat and dissipates oxygen, removing two of the required four ingredients for a fire, and also leaves no residue
What are the four distinct stages of a fire?
Incipient, smouldering, flame, heat
What is the incipient stage of a fire?
No visible smoke, flame, or heat. Produces ‘aerosols’ (very small changes in particles).
Ionization detector is used on this stage
What is smouldering stage of a fire?
Smoke, but no heat or flame. A fire can smolder for hours. Smoke detector is used for this stage.
What is the flame stage of a fire?
Visible flames, more heat but very little or no smoke.
UV/IR detector would be used in this stage
What is the heat stage of a fire?
Lots of smoke, flame, and heat, as well as toxic gasses.
Transition from stage flame to heat is flashover
Heat detector would be device used
Why is smouldering the deadliest stage of a fire?
Smouldering consumes oxygen and replaces it with toxic gases such as carbon monoxide, formaldehyde, hydrogen cyanide
Who determines the type of FA system used in any building?
BC Building Code. Determined by size of building and type of occupancy
Who publishes the standards for device installation and verification testing?
Underwriters Laboratories of Canada (ULC)
Who gives power to inspect FA installations for compliance?
BC Fire Marshal Act
Who is the Authority Having Jurisdiction?
BC Fire Marshal Act
Which section of the BC Fire Code outlines timelines for fire extinguisher inspection?
Section 6.2
Visually inspected monthly, professionally tested annually
Which detectors from the four stages of a fire are considered life saving devices?
Devices from stages 1 and 2
What does Fire Safety System mean?
Any system whose primary function is to warn against, prevent, or minimize the spread of fire, help evacuate the building occupants and contain or extinguish the fire.
What are the three types of fire safety systems?
Architectural, Mechanical, and Electrical
What is the architectural fire safety system?
Containment, fire resistance rating of structure
What is mechanical fire safety systems?
Automatic extinguishing systems, standpipe and hose systems, smoke removal
What is the electrical fire safety system?
Fire detection and alarm systems, emergency exit lighting, elevator recall
Which standard references How many, where, and how to install system components?
CAN/ULC S524 Standard for the Installation of Fire Alarms
Which standard tells how to verify systems?
CAN/ULC S537 Standard for the Verification of Fire Alarm Systems
What are the major groups of classification of buildings?
Assembly, institutional, residential, business and personal service, mercantile, industrial
When is a FA system required regardless of building classification?
-More than three storeys
- Occupant load larger than 300 excluding open air stadiums
- College or childcare facility with occupant load of more than 40
- Contained use area like prison
- Rec buildings or dining halls
- Licensed beverage establishment with occupant load of over 150
- Industrial areas
- Residential occupancy with sleeping acommodation for more than 10 people
What are the three main parts of every FA system?
IDCs, Control Panel, SDC’s
What is an IDC and its function?
Initiating Device Circuits.
- Acts an input to FA control unit
- Mostly automatic detectors like heat, smoke, or flame detectors
- Flow switch responds to movement of water inside sprinkler pipes.
- Integrated with systems like pull stations
What is an SDC and its function?
Signaling Device Circuit
- Acts as output
- Produces audible and/or visual alarm ex) bells and speakers, strobes, sirens
- Used to stimulate eyes and ears
What are the main functions of the FACU?
- Accept low current signals from initiating devices
- Operate audible and visual signal devices
- Provide electrical supervision of all field wiring
- Perform other ancillary and auxiliary functions
What are the two sources of energy required for FACU?
Primary and Standby
What is Primary Power?
Hard wired, AC connection to power
What is Standby Power?
Battery backup system. If power is lost for 15 seconds then backup/standby power comes on
What are Annunciators and their function?
- A visual/audible device that indicates alarms and other conditions. Located at the main entry of a building.
- Provides clear indication of zone and fault in the alarm system
What are Ancillary devices?
Building components and devices that are not part of the FA system, but controlled by it to serve life saving function
ex) Magnetic door latch, elevator recall or capture, mag lock release, damper control for HVAC, fan control
What are the requirements for a backup battery capacity?
Able to be in standby mode for 24 hours, and in alarm for 5 minutes
What is an Auxiliary Circuit?
Ties from the FACU to the City-tie module (CTM). Upon activation of alarm, relay will notify the monitoring service/fire department
What are the three types of communication styles for FA systems?
Simplex, Half-duplex, Full-duplex
What is simplex communication?
One directions, sends > receives
What is half-duplex communication
Exists between the FACU and the remote annunciator. Can be in both directions but only one direction at a time.
What is full-duplex communication?
Exists between FACU and all firefighter telephones in a system. Communication in both directions at the same time
What are the two signalling terms?
Alert signal, alarm signal
What is an alert signal?
Audible signal to advise designated persons (20 strokes per minutes)
What is an alarm signal?
Audible signal throughout building to advise occupants of a fire (bell is 120ppm, strobe is 1-2p/s)
What is a single-stage system?
- Activated initiating device sounds a general alarm on all signal devices.
- Found in areas where people are able-bodied and familiar with exits like apartment buildings or schools
- Operate the CTM and all ancillary devices
What is a two stage system?
- Alert signal will sound upon operation of any initiating device, advises supervisory staff.
- First-stage alarm (alert signal) will alert for a max of 5 minutes before alarm signal
What is a coded signal?
Pattern of the ringing within the first minute of operation. Indicates the zone, and may be used to indicate safe evacuation route. Code is repeated four times and then regular alarm sounds
When a single or two stage system is said to be indicating, what does that mean?
Means that there is use of a remote annunciator
What are initiating zones?
Circuits wired to field devices like smoke detectors, pull stations. Activation of these IDC’s will cause audible signals
What are supervisory zones?
Circuits wired to devices like sprinklers, flow switches. Activation of these devices will not cause alarm to sound, but will activate supervisory condition in system at FA panel.
What is a restorable heat detector?
Operate on bi-metalic strip. When temperature returns to normal so will the bi metallic strip
What is a non restorable heat detector?
Spring loaded plunger held under pressure by a spot of solder and connected to a heat collecting fin. Solder spot will melt and release the plunger against the NO contact creating an alarm. It cannot be reattached.
What is a dual-action heat detector?
Also called a rate-of-rise detector.
- Made of both non-restorable fixed temp and self-restoring elements
- air chamber allowing up to 8 degrees of temp increase Anything higher than 8 degrees will trigger alarm
What is the advantage of rate-of-rise detectors?
They are faster than just fixed temp sensors (non-restorable)
What are the temperatures for a fixed temp (non-restorable) detector?
58 degrees or 88 degrees
What is not a type of spot-type fire protection?
Linear heat detection
What is liner heat detection?
Two steel conductors with a heat sensitive polymer sheathing, when heat from fire reaches cable it will melt the polymer and the two conductors will short together. Alarm will be triggered, evacuation bells and suppression systems activate
What is a thermistor core linear heat detector?
Single conductor instead of two conductors. Thermistor core has a negative temp co-efficient, when it gets hot the resistance decreases, allowing more current through. FACU senses too much current and sends an alarm
What is the make up of a thermistor core lthd?
Centre conductor, ceramic core, stainless steel tubing on the exterior
What are the two types of smoke detectors?
Ionization (stage 1 - incipient) and Photoelectric (stage 2 - smoke)
How can smoke spread be controlled by the panel?
IDC’s activated, can cause closing dampers on ducts, activate exhaust fans, pressure fans in stairwells, release magnetic door holders
How does an ionization smoke detector work?
Made up of a chamber with a positive plate and negative plate, and radioactive plate at the bottom. The radioactive plate ionizes the air between plates, creating both negative and positive ions. When smoke enters the chamber, it interferes with the neutralization of the ions from the radioactive plate, causing a current decrease. Decrease in current will cause alarm condition.
What is the pro and con of ionization smoke detectors?
Pro - the fastest acting smoke detector
Con - Can have false alarms from dust or moisture, and must be replaced every 8-10 years
What are the two types of photoelectric smoke detectors?
Light scattering/reflected light, light obstruction
Which smoke detector is a stage 1 detector?
Ionization detector
Which smoke detector is a Stage 2 detector?
Photoelectric Detectors
- light scattering/reflected light
- light obstruction
What is the difference between a smoke alarm and smoke detector?
- Smoke detector is only a sensing device. Detects smoke and sends signal to a buildings fire alarm system which activates audible and visual alarms.
- Smoke alarm are stand alone systems that detect smoke and also give off audible alarms, like what is found in a residential settings.
Are smoke alarms considered fire alarm system devices?
No, they are not connected to a fire alarm system (they are stand alone devices)
What is a projected beam detector?
uses a transmitter and a receiver, passes both UV and IR beams, when there is smoke the UV light will be blocked and therefore the circuit cannot be completed and will signal an alarm condition
Where would projected beam detectors be used?
In buildings with very high ceilings, in high turbulence/industrial areas, in historical buildings
What is the only device that can protect against Stage 3?
Flame detectors/UVIR detectors
What is a UV/IR detector?
Line of sight or fire eyes detector. Detects a naked flame at about 5-30hz, always triggers a suppression system as they are considered property protectors
What are flame detectors best used for?
Large open areas, best detect flammable liquid fires. Fuels that burn blue will be picked up by the UV detector portion, fuels that burn red will be picked up by the IR detector portion
How are SDC’s set up in normal operation?
Signal devices are in reverse bias, the diodes will not conduct. Source is connected - to +, and an EOL is used.
How are SDC’s set up in an alarm condition?
The FACU will reverse the polarities of the source terminals, diodes now become forward bias, current flows through all SDC’s as they are in parallel with the 24VDC
What are the five types of signalling devices?
Vibrating Bells, Chimes, Horns & Sirens, Single-Stroke Bells, and Speakers
What is Temporal Pattern of Sound?
Standardized sound pattern for evacuation alarm signal.
Three pulses at 0.5s each, off for 1.5s, repeat
What are some visual signalling devices?
Strobe, rotating beacons, fire-do not enter sign
What is the height requirement for mounting audible signal devices?
Not less than 2300mm above finished floor.
If the height of the ceiling is low, devices should be installed at least 150mm below ceiling
What are the mounting requirements for visual signal devices?
Entire lens must be between 2000 and 2400 mm above finished floor. Also applies to combined audible and visual devices
What is the candela requirement for visual signals?
Not less than 15 candella
What is Class B wiring?
Two wires run through devices from FACU to EOL. Wiring is supervised because panel looks for resistance
What is Class A wiring?
4 wires run to and from devices. When last device is reached the two wires go back to FACU. Each device fed from two directions
What is the Class B IDC normal condition current value?
Approx 40mA
What is the difference between ‘alarm’ and ‘trouble’ in a Class B IDC wiring?
Alarm - When there is a short circuit in one of the devices, there will be a spike in current and equal voltage returning because the EOL is bypassed.
Trouble - if there is an open or ground fault in the circuit, there will be no voltage return because the circuit is now open (no power to devices or EOL)
What is a pro and con of Class B IDC wiring?
Pro - Simple to install, easy to understand
Con - devices downstream of the fault device do not operate, potentially putting lives at risk.
How does a Class B SDC operate compared to a IDC?
Operates the same in terms of the EOL ‘alarm’ and ‘trouble’ circuit, but uses an Internal Alarm Relay inside of the FACU at the SDC module.
Normal operation will have supervisory circuit connected to 24VDC, and signal power disconnected, when an IDC is activated the IAR will switch the polarity of the signal device. Supervisory circuit is now disconnected and the signal power is connected to 24VDC, EOL is disconnected.
Which class of wiring is called loop wiring?
Class A
Which class of wiring is called radial wiring?
Class B
Why is Class A advantageous over Class B wiring?
When a device is in alarm, all devices downstream continue to work/monitor, no life is in jeopardy
Is T-Tapping permitted in conventional wiring methods? (Class A and B)
No, t-tapping bypasses the electrical supervision
What is a CPU?
Central Processing Unit, it is what the FACU is referred to in addressable systems, because it now acts as a computer
How do zones differ from conventional and addressable wiring methods?
In conventional, zones are made physically with an EOL in each zone. In addressable, zones are created through programming and can contain many different devices (no EOL resistors)
What type of memory does the CPU store?
non-volatile memory - contents are not lost during power failure.
Firmware - permanent on FA systems, contains overall framework program
Software - building-specific to the application. Includes instructions to activate the ancillary relay outputs
What are the pros of addressable FA systems?
- More flexibility for operations (timers, counters, logic functions)
- Reduced power requirements
- reduced field wiring due to multiplexing
- easier to pinpoint alarms and troubles (each device has its own address)
- easy to expand systems and add devices
What are the cons of addressable FA systems?
- Easily damaged by static electricity and power surges
- Sensitive to electrical noise from power conductors
- Incompatible with other addressable systems (not interchangeable with brands)
What is device polling?
CPU asks the field devices one at a time “who are you?” and “what is your status”. Starts at device 1 and goes through each device, once it reaches the last device the cycle restarts.
What is automatic addressing?
On start up devices on the data loop will configure themselves. Used in small systems. Cannot T-tap in automatic addressing. New device would have to be added at the end of the loop.
What is manual addressing?
Setting dials or dip switches on devices, keep a record of device barcodes for programming. These devices may be t-tapped from any point. Devices do not need to be sequential, just unique from each other.
What is baud rate?
The speed of a digital signal from device polling. The number of devices can slow down the baud rate
How is the baud rate increased or kept at an acceptable level?
Transponders are used in addressable systems, installed at the start of a zone. Transponders act as ‘mini-panels’ they poll all devices downstream, and then CPU can poll the transponders - increasing polling baud rate
What are line isolators/fault isolators?
Used between floors or between each 2000m squared floor area. Iso mod’s disconnect a faulty section of a loop without interruption remaining sections of normal operation.
Ex) if there is a fault on floor 2, floor 1 and floor 3 will will be operational.
Do addressable CPU’s use 24VDC and 40mA?
No, they use data - binary 0’s and 1’s
In the binary system addressing, the first digit represents what?
Status.
1 = Normal
0 = Alarm
No address = Trouble
In the binary system addressing, the last 7 bits represent what?
The device address
What is the max amount of devices for a DCL-B?
200
What is the difference between DCL-A and DCL-C?
DCL-C uses line isolators to re-route the data if an open/short occurs
What are the four types of sprinkler systems?
- Wet-pipe
- Dry-pipe
- Pre-action
- Deluge
What are wet-pipe systems?
Fastest acting sprinkler system. Used on ordinary combustibles and where freezing isn’t a problem (indoors in offices/schools)
What device can sprinkler systems replace?
Heat detectors
When a flow switch is activated, what happens?
Sends alarm condition to FACP. Should occur within 90 seconds
Which system are flow switches used in?
Wet-pipe systems
Which systems are pressure switches used in?
Dry-pipe, pre-action, and deluge
What is the purpose of a pressure switch?
Gives alarm on loss of pressure
The flow switch works with a tamper switch, what is a tamper switch?
Activates a supervisory condition at the FACP. Supervisory indicated a trouble, but not an alarm. Wired in series with contact of flow switch, and wired in Class B conventional wiring. Switch will be ‘open’ if the cover of the flow switch is removed/off. Switch will be ‘closed’ if the cover is on the flow switch
What is water hammer?
A pressure surge in a pipe when water changes direction or velocity. Also called hydraulic shock
What is a jockey pump?
Boosts the water pressure in a sprinkler system. Typically have their own supervisory circuit in the FACU
What is a dry-pipe system?
Used where freezing is possible (outdoor parkades, warehouse etc) Contains air or nitrogen.
What is the water pressure in a dry-type sprinkler system?
150 psi
What is the air pressure in the dry-type sprinkler system?
45 psi
Dry side has ____ the surface area of the wet side
3-5 times
What is a pre-action system?
Similar to dry-type, but water is held back by an electronically controlled valve connected to FACU.
A pre-action system is double-interlocked, what does that mean?
Broken sprinkler head and IDC activation activates the sprinkler system
Where are pre-action sprinkler systems used?
In sensitive areas where accidental water damage would be extensive. ex) libraries, tech or data centres
What is a deluge system?
Used in high-hazard areas, pipes are dry and unpressurized, sprinkler heads are already open, connected directly to a water source and held back by a water valve.
How does a deluge system work?
When fire is detected, water is pumped through pipes and discharged through open heads.
Which sprinkler system uses foam based agents?
Deluge
When testing a Class B IDC with ohmmeter, what should the reading be if the system is good?
Whatever the EOL value is
What is the divide and conquer ts method?
Split the circuit in two, add and EOL at the FACU end, read which side has a low ohmmeter value and then follow that direction to find your fualt
When testing a Class A IDC with an ohmmeter, what should a good reading be?
Add an EOL into the FACU at the IDC module, the ohmmeter should read whatever the EOL value is.
How do we verify the SDC’s?
Connect ohmmeter, it should read whatever the EOL value is. Switch the leads, ohmmeter should read under 500 ohms.
when testing a Class B SDC, if both your ohmmeter readings are under 500 ohms, what is the likely cause?
One of the modules is wired in reverse
If there is a fault after energization, reset it in the control panel, if the fault stays/comes back, what is the problem?
The problem is in the control wiring
If there is a fault after energization, reset it in the control panel, if the fault clears, what is the problem?
The field wiring
How should shields be tied together in FA cable?
Shields tied together in the field, not grounded. Only Ground the shields/drains in the FACU
What is the most common type of storage battery for control units?
sealed lead acid
What is RTI?
Response Time Index. the measurement of speed of response of the detector. The lower the number, the faster the response. Scale is between 1 and 100
Ex) heat detector with RTI of 5 is faster than one with an RTI of 50
