IONIZATION VS PHOTOELECTRIC

IONIZATION VS PHOTOELECTRIC

The two most commonly recognized smoke detection technologies are ionization smoke detection and photoelectric smoke detection.

Ionization smoke alarms are generally more responsive to flaming fires.
How they work: Ionization-type smoke alarms have a small amount of radioactive material between two electrically charged plates, which ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the flow of current and activating the alarm.

Photoelectric smoke alarms are generally more responsive to fires that begin with a long period of smoldering (called “smoldering fires”).
How they work: Photoelectric-type alarms aim a light source into a sensing chamber at an angle away from the sensor. Smoke enters the chamber, reflecting light onto the light sensor; triggering the alarm.

For each type of smoke alarm, the advantage it provides may be critical to life safety in some fire situations. Home fatal fires, day or night, include a large number of smoldering fires and a large number of flaming fires. You can not predict the type of fire you may have in your home or when it will occur. Any smoke alarm technology, to be acceptable, must perform acceptably for both types of fires in order to provide early warning of fire at all times of the day or night and whether you are asleep or awake.

The best evidence has always indicated that either type of smoke alarm will provide sufficient time for escape for most people for most fires of either smoldering or flaming type. However, research is ongoing, and standards are living documents. If at any time, research points to a different conclusion, then that will lead to proposals for changes in the NFPA standard or the closely related Underwriters Laboratories standard for testing and approving smoke alarms. Both organizations currently have task groups looking at smoke alarm performance in the current home environment.

Digital Signage

Digital Signage Capacitive Touch Technology

With the development of science and technology, capacitive touch screen is known to the public. In the foreseeable future, it will replace resistive touch panel, and gradually catch up with Infrared Touch panel. Capacitive touch screen will dominant the market in the future, and mainly depends on its own merits as follows:

·         Capacitive touch screen generates signal only by touching instead of pressure.

·         In the production of capacitive touch screen, it doesn’t need calibration or just need one-time calibration, but resistive screen requires regular calibration.

·         Life span of the capacitive touch screen is much longer, because the capacitive touch screen parts no need movement.

·         Capacitive performs better than resistive touch on the optical loss and power consumption.

·         Capacitive touch screen is better in wearing resistance, long life, low maintenance costs compared with the resistive touch screen.

Fire alarm design category LD3 residential

Fire alarm design category LD3 residential

A Category LD3 fire alarm system is intended only to protect circulation areas that would be used as escape routes, by giving a warning if smoke is detected in these areas, so that occupants can escape before heat or smoke make this impossible. Therefore, the fire detection is positioned on the escape routes.

A Category LD3 fire alarm system cannot be expected, with any degree of reliability, to protect people who might be involved with the fire at ignition or in its early stages. This Category of fire system might not therefore prevent the death or serious injury of occupants in the room where the fire originates; it is intended only to ensure escape for those not immediately involved. If no fire detector is installed in the room in which fire starts, the time available for evacuation of other areas once fire is detected in the circulation area might be quite short. 

In a large family house adapted to provide accommodation for several households in separate self-contained units (a house in multiple occupation), a fire in one dwelling unit can be a hazard to occupants of other units. 

In this case, the fire detection and fire alarm system normally needs to extend across the boundaries between occupancies or be interconnected with systems in other occupancies. In practice, it is often appropriate for there to be a single integrated fire detection and fire alarm system that will alert all occupants before a fire in any dwelling threatens the communal escape routes, and that will provide early warning of any fire that starts in these escape routes. This objective is additional to that of enabling occupants of the dwelling in which fire starts to escape before their escape routes become impassable owing to heat or smoke.

In the case of purpose-built flats or sheltered housing, the degree of compartmentation between occupancies is normally sufficient to ensure that fire is contained in the dwelling of origin for a prolonged period. During this time, other occupants can remain in reasonable safety within their own dwellings. Accordingly, this part of BS 5839 does not provide recommendations for fire detection and fire alarm systems that incorporate detectors in the communal areas or ancillary accommodation (e.g. plant rooms) within purpose-built flats or sheltered housing. If, however, the provision of detection in these areas is considered desirable, it is essential to refer to the guidance contained in BS 5588-1, and it is appropriate that such fire detection and fire alarm systems comply with the recommendations of BS 5839-1.

BS 5839: Pt.6 covers the following domestic building types:
Bungalows
Multi-storey houses
Individual flats
Individual maisonettes
Mobile homes
Individual sheltered accommodation as well as their common parts
Houses in multiple occupation (HMOs)
Certain NHS housing in the community
Mansions 
Shared houses 
Houses divided into several self-contained single-family dwelling units

Not included are hostels, caravans, boats (other than permanently moored) and communal parts of blocks or flats or maisonettes.

BS 5839: Pt.6 is primarily concerned with saving lives and reducing injuries. However, it does contain within it recommendations for helping to reduce property damage too. Good fire safety practice and adherence to the Code can give the best possible early warning of fire and so reduce the financial impact as well as human suffering.

Mains Powered Smoke Alarms with Back-up Battery - Grade D

The problems outlined above can be overcome by using mains powered alarms that incorporate, within each alarm, a stand-by supply such as a primary or rechargeable battery. The alarms have to be interconnected either through wiring or radio-interlink. The mains power supply can come from a dedicated power supply directly from the fuse box or from the nearest permanently powered light fitting, as long as the smoke alarm heads can be removed without removing the base as well.

Grade D is required for new, owner-occupied buildings of up to three storeys, two storey rented properties and existing, owner-occupied buildings of more than two storeys. Very large storeys (>200m2) might require Grade B alarm system.

A question remains for landlords - can they be sure that their tenants are paying their electricity bills? Given that many tenants may have low incomes (in many local authorities, 70% or more of all tenants are on subsidised incomes), they may well experience periods of disconnection - and yet the landlord could well be liable if the alarm fails to sound because the tenant has not paid his or her bills! Unfair or not, as the law stands, it obviously makes good commercial sense to ensure that a reliable, ideally re-chargeable and sealed-in backup battery is in place.

The minimum back-up duration recommended is 72 hours, and the Code acknowledges that there could well be circumstances where a longer stand-by period is justified e.g. tenants' inability to pay their electricity bill.

False Fire Alarms Five Lessons to Learn

False Fire Alarms: Five Lessons to Learn

Successful fire detection has helped to reduce the number of fire deaths. But fire detection and alarm systems (FDAS) are also responsible for a large number of false alarms – 293,100 were recorded in 2011/12 alone.

Estimated losses of around £1bn a year have been attributed to false alarms, due largely to the disruption and loss of productivity in businesses.

1. Smoke detectors and age of components

Optical smoke detectors were responsible for 74% of the live false alarms observed during study.

The majority of these were due to cooking, dust, aerosol and steam. Although 74% may seem high, this type of detector is probably the most common type installed in the field.

Stringent false alarm tests may be necessary to force manufacturers to develop more sophisticated smoke detectors with greater immunity to false alarms.

2. Manual call points (MCPs)

False alarms generated from the misuse or accidental operation of manual call points have been observed during a previous BRE study. It was found then that the use of protective covers could reduce false alarms by up to 17%.

False alarms resulted from physical impacts to the sides of the MCP, and other accidental activations as well as malicious (or even ‘good faith’) intent.

Here, false alarms could be reduced by installing covers that require a dual action: lifting the protective cover has to be followed by activating the MCP mechanism.

3. Sprinkler flow activation switches

A drop in water pressure from an activated sprinkler system can cause a signal to be sent to the fire alarm system.

These signals can be sent erroneously from sprinkler systems during servicing or when local changes occur, such as a drop in pressure in the water mains.

Due to the complexity of fire sprinkler systems, more research has to be done before detailed recommendations for reducing false alarms in this area can be made. However, the use of a suitable signaling time delay may in some cases be effective.

4. Procedures dealing with false alarms

Where there were procedures for dealing with fire alarm activations, in 88% of cases they did not address false alarms, and in 93% of cases fire alarm contractors had given no false alarm advice.

Clearly, this demonstrates a need for more training for the people responsible for writing procedures, and for a greater exchange of false alarm information.

Further research work could be used to provide valuable guidance on how to reduce false alarms to a much wider audience. Frequent meetings between stakeholders are recommended to support this.

5. Multi-sensor detectors

None of the false alarm observed came from multi-sensors. This finding is encouraging and suggests that multi-sensors do not cause many false alarms.

However, the BRE alarm specialist cautions, that there are many different types of devices, each with their own false alarm rejection criteria, which could produce a broad range of alarm responses.

Some multi-sensor detectors may be set up to respond to one fire phenomenon only (e.g. steam). This would mean that, though less prone to producing false alarms, they may also be less sensitive to detecting certain types of smoke.

Further research is required to support the use of multi-sensor detectors. The findings should then be used to inform codes of practice and building regulations.

Engineered Smoke Control Systems

Engineered Smoke Control Systems

Smoke control systems use any and all methods possible to protect from smoke spread.  Doors, fans, sprinklers, dampers, and alarms are unified into one coordinated system.  Coordination of all the smoke control tactics is typically performed by a fire alarm/smoke control panel.  In most systems, fire fighters have override control from a Fire Fighters’ Smoke Control System (FSCS) Panel located in a lobby or a protected area.

Overrides and status indication of all equipment are present on the face of the FSCS or a computer screen display.  Figure to the left shows a detail of a typical override switch and indicator lights on a FSCS panel.

Smoke control tactics

Where strategy looks at the overall picture, the individual tactics are used to achieve the goals. The main purpose of this booklet is to explain details of how these mechanical and electrical systems operate with respect to dampers. The Fire Marshals, Building Officials, design engineers, and contractors are often called upon to go beneath the overall operation of a subsystem and look at the details.

Where devices and wiring interconnect two disciplines, there is a tendency for those involved to have only a fuzzy concept of the whole, interrelated design.

Some system dampers are applied in other ways to control air flow and smoke. Air Handling Units (AHU) are often shut down if any smoke detector in the area they serve senses smoke. However, in engineered smoke control systems the fans may continue to run while the AHU dampers position so that all return air is dumped outside and only fresh air is brought into the building. For large spaces that exhaust smoke in case of an event, dampers located on outside walls (with ducts where appropriate) open to allow outside air to enter to replace air and smoke pulled out by exhausts.

Figure 1: Relief damper variation of stairwell pressurization.

Smoke exhaust or extraction

In large spaces, there is no way to pressurize the large area to prevent smoke movement into the space. It is best to exhaust high volumes to remove the smoke. Atria and large spaces, particularly malls, have exhaust fans to remove smoke and keep it at least six feet above the occupied levels for 20 minutes to allow escape. Lower level make-up air dampers open to the outside to admit fresh air to replace the smoke.

Smoke vents

In certain warehouse and storage occupancies, smoke vents are prescribed by the codes. These can be automatic or manually operated. The goal is to remove hot, buoyant smoke to provide clear air for occupants and fire fighters. When wind is a potential problem, powered fans are used. These are part of an engineered system with the switches to operate them located outside the building where the fire service has quick access. (Section 910. IBC2009.)

Smoke shafts

In some buildings there are shafts extending the height of the building. Fans are mounted at the top and closed dampers are mounted in the wall of each floor. In case of fire, the fan turns on and the damper on the fire floor opens. Smoke is pulled out of the fire floor. A variation of this is the use of the HVAC ducts to pull smoke out of a building by sucking with the return air fan and opening the exhaust damper and closing the return air damper. The HVAC components are not typically designed for this application and the volume of smoke removed may be insufficient.

Zoned smoke control.

In some buildings entire zones or floors are exhausted or pressurized to prevent smoke migration. The fire zone or floor is placed under a negative pressure, often by the HVAC return duct damper and fan. The adjacent floors are placed under a positive pressure to prevent smoke migration. This is a “sandwich pressurization system.” If all the floors except the fire floor are positive, the system is known as a “building pressurization system.” Zoned smoke control was mandatory in high-rise buildings in the legacy codes, but the present IBC does not require them. They may still be found in some local codes and in underground buildings which are particularly dangerous since escape paths are highly restricted. See Below Figure.

Corridor pressurization

If only the corridors are zone pressurized as above, the system is called a corridor pressurization system. When smoke fills a corridor, it is very hard to see exit signs and people become disoriented. A combination of intake and exhaust fans can clear smoke. Corridor dampers normally provide ventilation air and exhaust stale air. However, they can be converted to smoke control dampers very easily. If a fire starts, the floors above and below the fire floor open their corridor ventilation dampers 100% to pressurize the floors while they close their return air dampers. This is identical in concept to the floor pressurization system discussed above. See Figure below.

Supply and return ducts in corridor protected by fire & smoke dampers.

Stairwell pressurization

The IBC requires that stairwells be designed as smoke proof enclosures. There are variations allowed by the code for when automatic sprinkles are provided and some architectural differences. Stairwell pressurization can be accomplished a number of ways. The IBC (IBC. 2012) requires vestibules in unsprinklered buildings.  This can be supplemented with stairwell pressurization.  In sprinklered buildings pressurization alone is allowed.  One should consult the IBC for details of requirements.

One method uses a constant volume fan capable of pushing air through any stair door that opens.  A barometric damper in the stairwell roof or wall relieves excessive pressure.  See Figure 1. In Figure 2 a combination vestibule with barometric is shown. There are designs by different fire protection engineers that use lobbies under positive pressure and others using negative pressure (IBC method) by exhausting. For the most part these designs do not use automated dampers in the periphery.

Since most buildings are sprinklered, pressurization systems alone are more common. A duct system can be run the height of the stairwell and proportional actuated dampers located every few floors with local pressure sensors.  If a floor door opens, the damper(s) nearest it modulate(s) open as necessary to maintain pressure.  A certain amount of smoke may enter the stairwell when any door is opened if there is a lot of pressure behind it.  Typically, the expansion of heated air does provide pressure.  It takes some time for the sensor, controller, and actuator to respond and open the local dampers further.  See Figure 3. The fan may be controlled by a VFD for better control.

Figure 2: Vestibule variation and supplemental stairwell pressurization

Other variations are possible and research is incomplete with regards to which is best in what geometric arrangement of stairs, stack effect, or height of stairs.  One variation is a second fan that turns on when the egress level door is opened.  Then that door does not relieve all the pressure necessary for the floors.  Some research has shown that sufficient ventilation alone during a fire will keep the stairwell tenable.  This employs a supply fan at the bottom of the stairwell and an exhaust fan at the top.  It can be combined with door pressurization by using variable frequency drive (VFD) fans.

Figure 3: Stairwell pressurization system using proportional damper control

Stairwells are built to be smoke proof compartments.  The occupants can escape into the stairwells and be protected from smoke while they escape the building.  When floor doors are opened, smoke must not enter the stairwell.  Since several architectural and control design methods are used examination of each system is necessary to understand its intent.  Testing using smoke generators helps to ensure the system works as required. Pressure in the stairwell must be below that which would hinder the opening of doors.

Elevator lobby pressurization

The lobbies of elevators can be pressurized to keep smoke from entering. These lobbies are sometimes areas of refuge and must be kept clear of smoke. The codes typically require that the elevator lobbies, where pressurized as a smoke compartment, be kept positive with respect to the occupied spaces. This is achieved by balancing the air systems to provide more air to the lobbies or by injecting air with a separate unit.

Special fire and smoke proportional or three-position actuators can be used to control the corridor dampers. The dampers must be partially closed for balancing, however they must reopen 100% to pressurize the floors adjacent to a smoke floor or to exhaust smoke as quickly as possible. Two speed fan motors or VFD’s prevent noise due to dampers that must be near closed during normal operation to avoid imbalance in design flow. Standard balancing dampers would restrict the full flow when needed. All other floors’ corridor dampers close so that a higher pressure and more air movement are available for the sandwich floors. Smoke causes most of the deaths in fires and smoke exhaust or pressurization methods can constrain it. However, in all of the methods discussed, too much oxygen cannot be injected and thus feed the fire. When fans are used to pressurize or add air for smoke removal, smoke detection on the inlet of the fan is used to avoid injecting smoke if the fire is near the inlet of the fan. Sprinklers are essential for fire protection. However, they are insufficient for fully balanced protection in large buildings. A balanced approach between active and passive measures produces the safest conditions. Compartmentation is the primary protection method for fire and smoke control. Maintaining the integrity of walls prevents fire passage and smoke spread. Containment duct and shaft dampers protect from smoke transport across compartment walls. About 85% of smoke dampers are used to maintain compartment containment. All means of egress must be protected – stairwells, elevator hoistways, lobbies, corridors, and paths to the outside. In addition, dampers are required where ducts penetrate shaft walls. Shaft dampers are the only way to restrict smoke movement. Air handling unit shutdown is insufficient alone. Large spaces like atriums, stages, malls, and stadium seating require smoke exhaust to keep the smoke layer above the level of the occupants’ heads. Engineered smoke control systems use mostly pressurization to prevent smoke migration. About 15% of actuated dampers are installed in them.

In general, any damper that is part of a smoke control system must be a UL555 (fire) and/or a UL555S (smoke) rated damper. In some cases exceptions are allowed since the damper is not meant to stop smoke. Examples are outside make-up air intakes and exhaust dampers on the outside of the building. They are usually open during an event and do not stop spread of fire and smoke.

Dampers are required to maintain compartmentation and restrict fire and smoke from spreading outside of the area of origin. However, full engineered smoke control systems can actively manage smoke and ensure means of egress for occupants. Exhausting large spaces with fans removes smoke. Preventing smoke from entering exit corridors, lobbies, elevators, and stairwells is critical in allowing escape. Other smoke control methods prevent the spread of smoke in buildings and along with architectural planning can protect occupants.

Smoke Alarm Maintenance

Smoke Alarm Maintenance

Smoke detectors are one of the most important safety devices you can install in your home to protect your personal belongings and your family. Once you've installed smoke detectors, it is absolutely necessary to test them regularly to ensure that they will sound during a fire. A great way to remember to change your smoke detector batteries in your home is to do so twice a year during Daylight Savings Time. When you reset your clocks forward or back, also change the batteries to keep your home and family safe!

You can keep your smoke alarm in its best condition using these tips.

• Keep smoke alarms clean. Dust and debris can interfere with the alarm’s operation so vacuum over and around your smoke alarm regularly.
• Once a month check the smoke alarm is working by pressing the test button. If you cannot reach the button easily, use a broom handle.
• If all is OK you will hear a loud beep or a series of beeps. If you get no response it is most likely the batteries, or the alarm if it is a long-life type, will need to be replaced.
• If a smoke alarm is not a long-life smoke alarm, its battery should be replaced every year. A good way to remember is to replace the battery at the same time every year, such as the beginning or end of daylight savings.

How long will my smoke alarms last?

You can expect your long-life smoke alarm to last for around 10 years. 
A smoke alarm is constantly monitoring the air in your home. At the end of 9 years after it has gone through over 3.5 million monitoring cycles, its components may become less reliable. As the detector gets older the chance it could fail to detect a fire increases. Smoke alarms that are wired into your electrical system (or burglar alarm) also need to replaced every 9 years.

Types of Smoke Detectors

When selecting a smoke detector, keep the following in mind: 

• Photoelectric units are better for smoldering fires, such as electric fires in the walls, so they are ideal for kitchens and bathroom where these fires tend to occur. 
• Ionization units give nearby air an electrical charge and then measure whether the charge stays constant or whether a fire is consuming oxygen in the air. These units are better suited to areas where fires get out of control, such as a basement near a furnace. 

Testing a Smoke Detector

To ensure that smoke detectors are working properly, test them on a regular basis. To do so:

• Press the test button on the unit and wait for it to sound.
• Light a candle and hold it six inches below the detector so the heated air will rise into the detector. 
• If the alarm does not sound within 20 seconds, blow out the candle and let the smoke rise. 
• If the alarm still does not sound, open the detector and clean the unit. Also make sure that all of the electrical connections are in good working order. 
• Then, test the unit again. If it is still not working, replace it immediately.

To stop an alarm sounding you need to clear the air in the sensor chamber. Fan the alarm with a paper or tea towel is the best method to stop the alarm automatically. Don’t try to disable the alarm by removing the battery.

Which is better, a conventional or addressable fire alarm system?

Which is better, a conventional or addressable fire alarm system?

Choosing a fire alarm system isn’t just about adhering to legal requirements; it’s also about saving time, money and effort.

The most common types of alarms that businesses use are conventional and addressable alarm systems.

Both types of alarm link input devices (such as call points and smoke/Heat detectors) to a main control panel. The main difference between the two is that with addressable fire alarm systems, you can pinpoint exactly which device has been activated.

How do addressable and conventional alarms differ?

Every device connected to the addressable system has its own unique address. When a fire is detected, the device’s address shows up on the main control panel, telling you exactly which device has been activated. This will enable you to find the exact location of a fire and extinguish them quickly.

With a conventional system, there is no way of pinpointing the exact location of the fire. However, by wiring your building into different zones, you can get a general idea of where the fire is. For instance, if you have two floors, you could wire the first as ‘zone 1’ and the second as zone 2. So if a fire occurs in zone 1, you know that the fire is somewhere on the first floor. 

Wiring differences

Addressable alarm systems connect devices using a loop. This is where one wire connects all devices to the control panel. Both ends of the wire loop connect to the control panel.

With a conventional alarm, each device will be connected to the control panel via its own wire, rather than a shared one. One end of the wire will be touching the device, and another touching the control panel. 

Which is the cheaper option for you? 

Conventional alarm panels cost a lot less to buy but are more expensive to install. This is because each device that is being connected needs its own wire. With addressable systems, one wire loop will connect several devices. This means conventional systems require more wire and more man hours during the installation phase.

Additionally, addressable systems have a range of other facilities that can help save money. For instance, addressable alarm panels monitor the air flow through smoke detectors to prevent the occurrence of false alarms, which can be costly to a business. 

Which is more reliable? 

The addressable alarm panel is also the more reliable of the two. This is because the wire connects to the control panel at both ends (see the diagram above). If one end of the loop becomes severed, signals can still be sent to the control panel via the other end of the loop. Loop isolation modules are also used to separate devices on the loop. This means that if one device becomes disconnected, it won’t disable the circuit. With a conventional system, if a wire has become severed, the device will become disconnected. 

Overall 
Functionally, the addressable fire alarm unit is superior, which can help prevent costly activities and save time when detecting a fire. It’s also cheaper and easier to install. But in terms of buying price, a conventional system is cheaper, and will meet the functional needs of small premises where a sophisticated system is not necessary.

Functional Testing of Multisensor detectors

Functional Testing of Multisensor detectors

The test fires that are used to assess ionisation and optical smoke detectors were developed in the 1980s.

The test fires used to assess smoke detectors

Current standards use the same methodology for identifying the most challenging conditions under which to test smoke detectors. Four test fires are used to assess smoke detector performance – these are

TF2: smouldering wood,

TF3: smouldering cotton,

TF4: flaming plastics and

TF5: flaming n-heptane.

The average smoke profiles produced from the four test fires are shown in Figure 1. The y-axis (m) represents the optical density (measured in dB/m) and indicates the larger particles which are generated in greater quantities during smouldering fires. The x-axis (y) is a dimensionless quantity that reflects the amount of ionisation taking place and represents the number of smaller particles which are generated in greater quantities during flaming fires.

Test Methodology

Twelve approved smoke detectors and smoke alarm devices from undisclosed manufacturers were used for the fire tests; eight of these were installed on the ceiling and four on an adjacent wall. The detectors comprised of eight domestic smoke alarm devices (four ionisations and four opticals) and four commercial smoke detectors (two ionisations and two opticals).

To define the end point of the tests, guidance was taken from current standards, which specify end of test limits for smouldering and flaming fires that are m=2 dB/m or y=6 respectively.

Test fires and detector responses

Twenty-nine test fires were conducted, including four test fires specified in current fire detection standards. Of these eleven were smouldering fires, sixteen were flaming fires and two started off smouldering and went on to become flaming fires. The fuels used included unleaded petrol, medium density fibreboard (MDF), PVC cable, flame retardant polyurethane foam, sunflower oil, newspaper, polyester, nylon, ABS, polystyrene, polycarbonate and polyethylene.

A smouldering fire test

All of the detectors were periodically replaced, as exposure to the smoke from a number of tests could cause contamination in the smoke chambers that could potentially affect their response.

A flaming fire test

Of the twenty-nine test fires conducted one produced too little smoke and could not be reproduced however five produced too little smoke and were repeated with greater quantities of fuel.  For the twenty-three complete tests, sixteen fell within the m/y limits specified in current standards. From these tests there were six no responses and 270 responses which represents positive responses 97.8% of the time. The six no responses are attributed to the inconsistent responses of one particular type of detector and suspected contamination for the remaining ones.

Even though no statistical data was gathered by repeating tests, the results do provide evidence of the response characteristics for the types of detectors (optical or ionisation) to a variety of smoke types produced from smouldering and flaming fires.

Conclusions and further work

The test fires TF2-TF5 do cover most general purpose applications as a real fire is unlikely to involve only a single type of material. As more materials with different smoke characteristics are involved in the fire the likelihood of detection increases.

However, it should be noted that smouldering fires can continue for a long time with only one material being involved, potentially leading to the production of toxic gases in fatal concentrations. An example is bedding in contact with a heat source such as a lit cigarette. In this case an ionisation detector may not respond and therefore should not be sited in locations where such a scenario is possible. In contrast a flaming fire in a building will eventually produce sufficient heat that will radiate onto other materials and lead to the production of smouldering smoke particles to which the optical detectors are expected to respond.

This research demonstrated that commercial and domestic approved ionisation and optical smoke detectors respond to a broad range of fires within and beyond the fire test limits of existing standards. The fire tests specified in current standards are considered to be appropriate and are sufficiently wide in terms of distribution of smoke characteristics. This demonstrates that the fire tests specified in these test standards are still applicable today and, despite the changes in the use of materials over the decades, approved smoke detectors have very wide smoke response capabilities.

Both ionisation and optical smoke detectors are attuned to detecting certain types of fires. In order to ensure that the most appropriate type of device is installed, guidance on the use of ionisation and optical smoke detectors should be sought from relevant codes of practice.

The increasing use of multisensor detectors in fire detection and fire alarm systems has lead to some discussion as to how they should be tested in the field.

The recommendations detailed below should be considered as the minimum for properly testing these complex devices:

1.    Multisensor fire detectors should be physically tested by a method that confirms that products of combustion in the vicinity of the detector can reach the sensors and that the detector responds appropriately. A test method purely reliant on an electronic and / or mechanical means is not sufficient to comply with this requirement.

2.    Due to the complex nature of multisensor fire detectors, they should also be tested in accordance with the manufacturer's instructions.

3.    Where the detector or system design allows each sensor on which a fire detection decision depends (e.g. smoke, heat, CO) to be physically tested independently, then these sensors should be physically tested independently.

4.    Alternatively, individual sensors may be physically tested together if the detection system design allows simultaneous stimuli and individual sensor responses to be verified either individually or collectively.

5.    Only where the detector or system design is such that individual sensors cannot be physically tested individually, for example certain types of conventional multisensor detectors, the primary sensor alone should be tested.

6.    The response to each test should be at least confirmed by the CIE.

7.    All tests and their results should be recorded.

EN 54 Fire detection and alarm systems

EN 54 Fire detection and alarm systems

The EN 54 Fire detection and fire alarm systems is a mandatory standard that specifies requirements and laboratory test for every component of fire detection and fire alarm system and it allows the free movement of construction products between countries of the European Union market.

It was developed and approved by European Committee for Standardization (CEN, French: Comité Européen de Normalisation).

This standard is widely recognized around the world for several countries outside of European Union. It is recognized in Latin American countries, Brasil, African and Asian countries and several islands in the Pacific Ocean.

According to the Construction Product Products Regulation, it is mandatory that Fire Detection and Fire Alarm equipment is certified under EN 54 standard by an authorized certification body.

(TC) Technical Committee CEN/TC72 Automatic fire detection system and fire alarm

It is the TC responsible of developing the normative for fire detection system in the EU and responsible for coordination with committees of each member country to update information and making new normative in fire detection system. The committee of each member country report and depend directly from CEN/TC 72. These committees must inform updates and new normative that is received from CEN/TC72 to responsible office, departments or national organization which has been managed the normative of Fire detection system inside of every member country. These national committees must carry the necessities and new requirement of the industry and user of each country member of Fire detection system to the CEN/TC72 that is the European Committee which is responsible of update and change normative of fire detection system in the European Union.

EN 54 Standard Family Parts

The standard has been published in a number of parts:

·         EN 54 part 1 Fire detection and fire alarm systems. Introduction

·         EN 54 part 2 Fire detection and fire alarm systems. Control and indicating equipment (Fire alarm control panel)

·         EN 54 part 3 Fire detection and fire alarm systems. Fire alarm devices. Sounders

·         EN 54 part 4 Fire detection and fire alarm systems. Power supply equipment

·         EN 54 part 5 Fire detection and fire alarm systems. Heat detectors. Point detectors

·         EN 54 part 6a Fire detection and fire alarm systems heat detectors; Rate-of-Rise point detectors without a static element.

·         EN 54 part 7 Fire detection and fire alarm systems. Smoke detector. Point detectors using scattered light, transmitted light or ionization

·         EN 54 part 8 Components of automatic fire detection systems. Specification for high temperature heat detectors.

·         EN 54 part 9 Components of automatic fire detection systems. Methods of test of sensitivity to fire

·         EN 54 part 10 Fire detection and fire alarm systems. Flame detector. Point detectors

·         EN 54 part 11 Fire detection and fire alarm systems. Manual call point

·         EN 54 part 12 Fire detection and fire alarm systems. Smoke detectors. Line detectors using an optical light beam

·         EN 54 part 13 Fire detection and fire alarm systems. Compatibility assessment of system components

·         EN 54 part 14 Fire detection and fire alarm systems. Planning, design, installation, commissioning, use and maintenance.

·         EN 54 part 16 Fire detection and fire alarm systems. Components for fire alarm voice alarm systems. Voice alarm control and indicating equipment

·         EN 54 part 17 Fire detection and fire alarm systems. Short circuit isolators

·         EN 54 part 18 Fire detection and fire alarm systems. Input/output devices

·         EN 54 part 20 Fire detection and fire alarm systems. Aspirating smoke detector

·         EN 54 part 21 Fire detection and fire alarm systems. Alarm transmission and fault warning routing equipment

·         EN 54 part 22 Fire detection and fire alarm systems. Line type heat detectors

·         EN 54 part 23 Fire detection and fire alarm systems. Fire alarm devices. Visual alarms

·         EN 54 part 24 Fire detection and fire alarm systems. Voice alarms - Loudspeakers

·         EN 54 part 25 Fire detection and fire alarm systems. Components using radio links and system requirements

·         EN 54 part 26 Fire detection and fire alarm systems. Point fire detectors using Carbon Monoxide sensors

·         EN 54 part 27 Fire detection and fire alarm systems. Duct smoke detectors.