Fire Detection

1. Conventional Fire Alarm Systems

 

In a Conventional Fire Alarm System, physical cabling is used to interconnect several call points and detectors, the signals from which are wired back to the main control unit. 

 

Call points and detectors are arranged in “Zones” to simplify locating the cause of the alarm, this is important for both the fire brigade and general building management.

 

Each zone is indicated at the Fire Alarm Control Panel either with an indicator lamp, a text display, or in some cases both.

 

It makes sense that the more we can divide a building into zones, the more accurate locating the alarm trigger will be.

 

The Control Panel is wired to a minimum of two sounder circuits which could contain bells, electronic sounders, or other audible fire alarm devices.

 

It is these devices that sound the alarm when triggered.

 

2. Addressable Fire Alarm Systems

 

The detection principle of an Addressable System is the same as a Conventional System except that each detector is given a set Address (usually by means of a dip-switch) and the Control Panel can then determine exactly which detector or call point has initiated the alarm.

 

The detection circuit is wired as a loop and up to 99 devices may be connected to each loop.

 

It is common for the loop to be fitted with Loop Isolation Modules so that the loop is sectioned in order to ensure that a short circuit or single fault will only cause the loss of a small part of the system; allowing the rest of the system to function normally.

 

3. Intelligent Fire Alarm System

An Intelligent Fire Alarm system, each detector effectively incorporates its compute

– Heat detectors

– Smoke detectors

– Carbon Monoxide detectors

– Multi-sensor detectors

– Manual Call Points

Heat Detectors

Heat detectors can either work on a fixed temperature basis, where it will trigger an alarm if the temperature exceeds a pre-set value or they can work on the rate of change in temperature. Commonly Heat detectors work in a similar way to an electrical fuse, the detectors contain a eutectic alloy which is heat sensitive when a certain temperature is reached the alloy turns from a solid to a liquid which in turn triggers the alarm

Smoke Detectors

There are three basic types of smoke detectors including:

– Ionization

– Light Scattering

– Light Obscuring

Ionization Smoke DetectorAn 

Ionization Smoke detector generally contains two chambers. The first is used as a reference to compensate for changes in ambient temperature, humidity, or pressure.

The second chamber contains a radioactive source, usually an alpha particle, which ionizes the air passing through the chamber where a current flows between two electrodes.

When smoke enters the chamber the current flow decreases. This drop in current flow is used to initiate an alarm.

Light Scattering Smoke Detector

The light-scattering smoke detector operates on the Tyndall effect; a photocell and a light source are separated from each other by a darkened chamber such that the light source does not fall on the photocell.

 

The passage of smoke into the chamber causes the light from the source to be scattered

 

The control panel monitors the initiating device circuits at all times for shorts and open wiring by means of the applied DC voltage. The initiating devices are normally open.

 

In the event of a fire they become conductive at close to zero ohms. How, then, is it possible for the control panel to differentiate between a non-alarm state and an open wiring fault? This is accomplished by means of an end-of-line resistor.

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The control panel also monitors the functionality of its own wiring and zone cards, and trouble is reported in the display.

Another capability of the fire alarm system is to call out in case of alarm. Two dedicated phone lines are connected, and the system performs test calls periodically in accordance with programmed instructions. If either phone line won’t connect, the system goes into the trouble state, so repairs can be made.

The essence of a fire alarm system, as opposed to individual smoke detectors, even if they are wired to indicate in concert, is that it is supervised from a central location. The whole notion of supervision is critical.

It does not mean that a person sits at the console and watches it at all times. What it means is that a supervisory voltage is applied to all circuitry, and current flow is monitored electronically to verify that equipment and wiring are intact.

If the system goes into alarm and won’t silence due to touchpad malfunction, for example, it can be disarmed after the zone is checked for fire by cutting off the power.

 

First, unhook one side of the battery array, then unhook the black-white-green incoming power connector. If a

These alarms may be activated automatically by smoke and heat detectors or manually by fire alarm activation devices such as manual call points or pull stations

Alarms can be either motorized bells or wall mountable sounders or horns. They can also be speaker strobes that sound an alarm, followed by a voice evacuation message that warns people inside the building not to use the elevators.

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

Why install a fire alarm system in Kenya?

A fire alarm system is intended to enable a fire to be detected at a sufficiently early stage so that people at risk can be made safe either by escaping from the fire or by extinguishing the fire (also to prevent extensive property damage). Neither of these measures can be used until people are made aware of the fire.

The effectiveness of the fire detection and alarm system depends on the stage of the fire at which it is operated. In order for all the occupants to escape without too much difficulty, an early alarm should operate before the escape routes become smoke-logged to such an extent as will cause occupants to have difficulty finding their way out of the building.

Fire Alarm Systems are used to protect life and property.

Fire alarm system accessories

• Initiating devices, capable of placing the system in the alarm state. These can be photoelectric smoke and heat detectors, ionization smoke detectors, heat detectors, in-duct smoke detectors, manually operated pull stations, and sprinkler water flow sensors.
• Indicating appliances, whose purpose is to announce building occupants or at a remote location when the system

If we talk about the main difference, it is related to how they transmit signals from connected devices to communicate to the main control panel. Cost is another factor that might be your deciding factor for the Fire alarm system that you choose.

 

Understanding the differences between the two in a better manner will help you pick out the best fire alarm system for your needs as well as your company’s requirements

 

Conventional fire alarm systems use analog technology and are hardware-based which are made up of zones. The zones connect the control panel.

 

These zones have multiple devices including initiating and notification devices. These zones, to communicate to the control panel use electrical currents.

 

To increase the amount of electricity flowing in the circuit, they use initiating and notification devices in case of an emergency or environmental conditions of fire such as heat and smoke, in the zones or area if the environmental conditions as sensed by the sensor exceeds a predetermined threshold.

 

This increase or change in the electrical current is communicated to the control panel to trigger the alarm. The control panel differ in the number of devices it can support, so conventional fire alarm systems are limited in a way that the individual circuits communicate to the control panel, but it depends on the number of devices it can support.

 

Another issue faced with conventional fire alarm systems is that it does tell us whether a device gets activated but you can’t determine which device and where throughout the area.

 

Addressable Fire Alarm Systems:

Addressable fire alarm systems use digital technology to transfer information.

 

 

• Automatic Fire Detectors: These detectors are placed throughout the building and come in various types, such as smoke detectors, heat detectors, and carbon monoxide detectors.
• Detection: When a detector senses smoke, heat, or carbon monoxide exceeding predetermined thresholds, it sends a signal to the fire alarm panel.
• Alarm: The fire alarm panel activates the building's alarm system, similar to a manual system.

 

 

• Manual Call Points (MCPs): These are the red break-glass boxes strategically placed throughout the building. When a fire is discovered, someone needs to manually break the glass and press the button inside the MCP.
• Activation: Breaking the glass triggers an electrical signal sent to the fire alarm panel.
• Alarm: The fire alarm panel activates the building's alarm system, sounding sirens or bells throughout the premises.

Pros of Automatic Systems:

• Faster detection of fire, especially in unoccupied areas or during sleeping hours.
• Provide earlier warning to occupants, allowing for quicker evacuation.
• Can be integrated with other fire safety measures like building ventilation shutdown or fire door activation.

Cons of Automatic Systems:

• More expensive to install and maintain compared to manual systems.
• Higher chance of false alarms due to environmental factors (dust, steam) or malfunctioning detectors.

But what is an Automatic Fire Alarm System and what are the differences between this and a Manual system?

In this article, we’ll provide the essential information and advice you need to keep your property safe and secure against the risks of fire, with an Automatic Fire Alarm System or a Manual Fire Alarm System. We’ll cover: 

 

• requirements for fire detection and alarm systems in Kenya

• What are Manual category fire alarm systems and how do they work?

• What are Automatic category fire alarm systems and how do they work? 

• How to improve Fire Safety in your business today

 

Requirements for fire detection and alarm systems Kenya

All businesses in Ireland are responsible by law for the health and welfare of their employees and any visitors to their premises, which includes providing the right fire safety systems, including robust and reliable fire detection systems.

 

The requirements for fire safety, including detection and alarm systems, are governed by The Fire Services Act 1981-2003 and the Building Regulations 1997-2017. This legislation outlines the need for a thorough fire risk assessment, who is responsible for fire safety on site, and recurring duties required for maintaining and recording fire safety protocols on your site.

 

When it comes to fire safety equipment, the Irish Standards for the design, installation, and maintenance of fire alarm and detection systems are also vital for business owners.

 

We supply fire alarm systems and fire suppression systems including conventional fire alarm systems, addressable fire alarm systems, emergency light systems, FM200 gas suppression systems, fire pumps, fire hose reels, and cabinets.

 

We have a team of qualified Fire alarms installations Experts, Both in House and outsourced all over Kenya to help you with any fire installation project.

 

A fire alarm and fire detection is a security setup that comes with a number of devices working together as a unit to detect and warn people in case of eruption of fire.

The warning is mainly through visual and audio appliances when smoke, fire, carbon monoxide or other emergencies are present. 

Some of these alarms come with inbuilt functionality that enables them to be activated automatically by smoke detectors and heat detectors.

There are some that need to be activated via manual fire alarm activation devices such as manual call points or pull stations. Alarms can be either motorized bells or wall mountable sounders or horns.