The importance of Manual Call Points
Even in the most sophisticated fire system installed in the most modern of premises, manual call points perform a vital role in enabling anyone to raise the alarm in the event of discovering a fire.
The activation of a fire detection system is achieved either automatically, initiated by a detector, or through a manual call point or pull station. Call points are used throughout Europe, Australasia and the Far East and pull stations are predominantly to be found in North America. Although the manual devices are very different in their design and operation, they are both the only Human Machine Interface (HMI) mechanism that an occupant of a building can use to activate the fire alarm system.
In certain circumstances, human intervention is going to be the fastest way of raising the alarm. For example, consider a boiler room, which typically will be protected by a thermal detector. If a slow smouldering fire was to develop, the thermal detector would take a very long time to respond, whereas someone entering the room will be able to react to the situation immediately.
Long before the development of smoke detectors in 1941, the break-glass call point was the only means of activating the simple fire systems of the time. Today’s intelligent automatic fire detection systems are complex arrangements of sophisticated detectors, high performance audible and visible warning devices and automated controllers for external systems such as air-conditioning systems, door controllers and other equipment, all managed by advanced software. The functionality and performance of detectors and warning devices in the system has significantly improved as the result of technology advances, and while superficially the manual call point would appear to be unchanged, in fact, nothing could be further from the truth. It too has moved a long way forward from the original design, in which, when the glass was broken, a spring-loaded switch was released into the operating position, activating the warning bells. In those days, it was, quite literally, a question of breaking the glass using the hammer attached to the device.
Forty years ago, in 1972, KAC Alarm Company came into existence to manufacture a completely new design of break-glass call points, in which the idea of scoring the reverse of the glass and using a protective film enabling it to fracture cleanly and safely was first introduced. The fracturing of the glass allows a microswitch to activate the system. This operating principle has been adopted as the de facto industry standard used by all manufacturers, and, together with the resettable version in which the operating element does not have to be replaced after use, is universally used in all installations.
Developments in call point technology have kept pace with the rest of the industry. In addition to conventional units, intelligent versions interface with the control panel through an embedded interface module, which, using the appropriate protocol for the system, enables the exact location of the device to be identified at the control panel.
Resettable versions, in which a plastic element drops down to enable the microswitch to operate when pushed, are a relatively recent development. In both types, replacement of the glass or resetting the plastic version requires a tool to be used by an authorised person. Pull stations operate somewhat differently; there are single-action units where the user pulls down a handle, and, more commonly, dual-action versions, where the user has to lift up and pull down or push in and pull down to activate the operating handle. Typically, pull stations feature a T-bar style pull, and, like call points, they have to be reset after operation by an authorised person using a tool.
In addition to break glass and resettable call points, other operating methods are widely used for specific applications. Key operated, push button and push button with protective cover units are all available from a number of manufacturers.
Arguably, the most important recent advances in call point design have been the development of environmentally sealed, explosion proof and intrinsically safe variants. IP66 or IP67 environmentally sealed units are housed in an enclosure that prevents water and dust from entering the call point. By providing devices that can be installed outside, in wet or dusty areas inside, or where equipment has to be hosed down for cleaning purposes, the fire system can be extended throughout the protected premises. In addition, good safety practice and legislation require an emergency stop mechanism to be installed on machine tools and other production equipment; waterproof call points are ideal for this requirement.
To install call points in hazardous areas, they must be either intrinsically safe or explosion proof. Hazardous areas are defined as areas where concentrations of flammable gases, vapours or dusts may occur, either constantly (Zones 0 and 20), under normal operating conditions (Zones 1 and 21) or infrequently (Zones 2 and 22). A whole series of additional conditions relating to the temperature classification and the auto-ignition temperatures of the type of gas or dust to be found ensure that any installed equipment will not initiate an explosion or fire. Hazardous areas are to be found in a very wide range of manufacturing industries, far beyond the obvious petrochemical plants. Food, pharmaceutical and cosmetic manufacture all involve processing potentially explosive substances, while the problems of explosions in grain silos and sugar processing plants are very well documented.
The difference between the two types is that the input energy entering an intrinsically safe device is constrained so that any arcing or sparking within the unit cannot generate enough heat to start ignition. In explosion-proof call points, the operating mechanism is mounted in an enclosure that is sufficiently robust to prevent any internal explosion from reaching the outside. While bulkier than intrinsically safe units, they are far more robust, enabling them to be installed in very demanding environments such as offshore oil platforms. Typically housed in a GRP or aluminium enclosure, they are environmentally sealed to IP66 or IP67 in order to achieve the explosion proof rating, enabling them to be installed in aggressive environments.
Other specialist options include call points that will switch up to 2A at 240VAC, enabling them to be used for replacements and extensions in the legacy mains voltage fire systems that are still quite common in many regions. While the operating methodology is the same, call point variants for particular applications are often colour coded for easy identification. The familiar red body is for fire systems; orange for smoke vent control, green for emergency door release, escalator emergency stop and similar uses, blue for security systems and yellow for extinguishing system activation or general evacuation signalling. To suit differing requirements, conventional call points are normally with single or double pole switches and a selection of different resistor values to suit the requirements of various control panel manufacturers.
Standards & Approvals
For fire systems, the relevant product standard for call points is EN54-11. Using approved devices is important in life safety systems; third-party testing by a reputable test house does far more than simply confirm the physical construction and operation of the device. Extensive tests for environmental factors such as operation at elevated temperatures, corrosion tests, EMC tests and shock and vibration are carried out, so a third-party test certificate gives the installer and user confidence that the device conforms in all respects to the requisite standard. Even if the installation code of practice does not make it mandatory to use approved devices, to use non-approved devices is a false economy that could potentially put life at risk if they do not operate when required.
EN54-11 defines a pictogram of a house that must be used at the top of the body of a call point and two arrows indicating the optimum point on the operating element. In some markets, supplementary wording is often added to the house pictogram to remove any doubt about the function of the call point. For other specialised applications, a legend is normally printed on to the call point to identify the function and the body colour will not be the fire system red. The legend will normally be in the form of wording, for example, “Emergency Door Release”, so the issue of different languages for specific markets immediately arises.
Call Point Siting
In buildings, call points must be installed at locations where they will be immediately obvious. The positioning of call points within premises is defined in the UK by BS5839 part 1:2002, the Code of Practice applicable to the installation of fire systems. All European countries have similar requirements, and although there are minor variations, there are generally few major points of difference. Manual call points should be mounted on all escape routes, and at all exit points from the floors of a building and to clear air, ensuring that occupants can leave the building quickly when necessary and activate the fire system while doing so.
It should not be possible to leave the floor of a building without passing a manual call point, nor should it be necessary to deviate from any escape route in order to operate a manual call point. Call points mounted at the exits from a floor may be mounted within the accommodation or on the stairwell. In multiple storey buildings, where phased evacuation is to be used, call points should be mounted within the accommodation to avoid activation of call points on lower levels by people leaving the building.
In order to provide easy access, call points should be mounted between 1.2 metres and 1.6 metres from the floor, and should be clearly visible and identifiable. The maximum distance anyone should have to travel in order to activate a manual call point is 45 metres, unless the building is occupied by people having limited mobility, or a rapid fire development is likely, in which case the maximum travel distance should be reduced to 20 metres. Call points should also be sited in close proximity to specific potential hazards, for example boiler rooms or paint spray booths, where an environmentally sealed unit will be required.
Choosing a Supplier
When deciding on which call point manufacturer to use, specifiers should consider a number of points:
• Are the products third-party approved to the relevant specification?
• Does the manufacturer produce sufficient variants to cover the requirements of the installation?
• Is the manufacturer set up to produce relatively small quantities of devices in various body colours and with custom legends at an economical cost?
• Is there a learning curve for the installation team because the design varies from type to type, or is the wiring interface constant across all versions?
• How is the manufacturer perceived in terms of product quality, delivery performance, technical support and overall responsiveness?
• Are the conventional products available through reputable channels and can the intelligent ones operate under the main detector protocols: System Sensor, Apollo, Hochiki, Nittan and others?
• How easy or difficult is installation?
• Can the zone or loop wiring be tested for open and short circuits after the first fix installation, or does the actual call point have to be installed?
There will be other criteria based on previous experience, but if the answers to the majority of the above questions are positive, it should be a good indication that the supplier is reputable and its products can be relied on to perform to specification.
To conclude, call points perform a vital role in even the most sophisticated fire system installed in the most modern of premises, enabling anyone to raise the alarm in the event of discovering a fire. In smaller systems, they can be the only method of raising the alarm. Wherever they are installed, they provide a highly visible reassurance for the occupants and visitors to the building that a fire detection system is present.
Resettable versions, in which a plastic element drops down to enable the microswitch to operate when pushed, are a relatively recent development.
Mark Thomson is Head of Marketing at KAC Alarm Company
For further information, go to www.kac.co.uk