Fire Detection and Alarm System or FDAS

I have a presentation to electronics engineering students in Iligan Institute of Technology – Mindanao State University, the title “ Fire Detection and Alarm System” or FDAS. Safety is a common word we hear in industries but some of the world seems to ignore this and the obvious reason was that the city enforcement of laws are weak. The goal was to spread the awareness on RA9292, the electronics engineering law inclusion to the National Building Code which is crucial to protect building occupants from harm and prevent damage to property.

There are 3 important phases of fire detection and alarm system; the time element, notification (manual and automatic alarm) and activation. The idea of FDAS was to sense signs of fire and alert personnel to prevent fire from getting bigger.

Why do we need FDAS when we already have some fire extinguisher?  To answer that question lets discuss the fire department response time. First the ignition where combustion starts and fire grows undetected. Then the fire will be discovered which depends on the time, location, etc. The call processing and dispatch time begins when the emergency call is answered and emergency res-ponders are dispatched, there are other activities when this happen. The turnout time begins when emergency res-ponders are notified and fire truck/support prepares to leave the station. The drive time begins when the fire truck leaves from station to the fire location. Arriving on the scene, fireman needs to pull hose lines, establish water supply, etc. before they could combat the fire and extinguish it. The damage could be well prevented if fire detection and alarm system are installed. Prevention is much better than fighting the fire itself, that why we need FDAS.

 

Block diagram of FDA system

Type of detectors
There are three broad classifications of fire detection; heat, smoke & flame detection. Fire detectors are used in a variety of fire prevention and in suppression system.

Fire detectors
Heat detectors respond to the excess heat generated in a fire. The most basic is fixed temperature type and detect heat by one or more of 3 primary principles of physics; expansion of heated material, melting of heated material, changes in resistance of heated material. The rate-of-rise type heat detector operate on the principle that the temp. in a room will increase faster from fire than from atmospheric temperature (specified rate of temp. rise –degrees/min) and will initiate an alarm when the rise in temp. exceeds 12-15F(7-8C) per minute or alarm can be initiated at a temp. far below that required for a fixed-temp. device.

The smoke detectors respond to the presence of smoke. The Photoelectric smoke detector uses a photocell coupled with a specific light source, it is basically smoke entering the smoke detector chamber disrupts the light beam causing an alarm signal to be initiated and it is more sensitive to smouldering fires. The Ionization smoke detector works when invisible products of combustion enter the chamber and decreasing the current between the -ve & +ve plates, thereby initiating an alarm signal. It generally responds faster to flaming fires versus smouldering fires and automatically resets when the atmosphere clears.

 

Projected-Beam Style of Photoelectric Smoke Detector

A projected-beam photoelectric detector activates when light is blocked by smoke from reaching a sensor.

Ionization Smoke Chamber
The flame detectors which detects flame using two type sensors, ultraviolet light and infrared. The Fire-Gas detectors which monitors levels of carbon dioxide and carbon monoxide (common to all fires), more discriminating than other detectors - can be designed to be sensitive only to gases produced by specific types of hostile fires and ignores gases produced by friendly fires. Lastly the combination detectors designed to have more than 1 function e.g. heat/smoke, smoke/carbon monoxide detectors, different combination make the detectors more versatile and more responsive to fire conditions.

We cover the types of detectors in specific areas and proper location where to put them. Including areas that they are not required.

Output devices
Audible output devices, an audible alarm signal to inform people that alarm is activated. This devices are installed inside or outside the protected area, based on the required level of protection. They can be sirens, bells, buzzers, horns, voice drives, etc.

Visual output devices, a visual signal lets personnel know the status of the alarm system if it is activated.  This devices are installed inside or outside the protected area, based on the required level of protection. These devices may consists of; strobe lights, LEDs, on/off printers, etc.

CCTV system, a CCTV can work as a video-based detector, depending on the type of camera and the software it runs with. The images from the closed-circuit televisions are sent to a computer with software designed to detect the characteristics of a flame/smoke.

Excerpt from the Philippine Electronics Code on the use of battery-operated smoke/heat detectors, PEC section 1.6.1;

Buildings, structures, facilities, houses, or premises… where more than 400sq.m in total floor area, not more than 2 floors or levels and with a height of not more than 10 meters may choose not to install FDAS. However each battery-operated devices must cover a floor area of not more than 50sq.m and each room shall be separately protected.

Areas where detection is not required

•  Toilet and /or bathroom with a floor area of less than 4sq.m
•  Exhaust ducts exhausting from toilets and/or bathroom
•  Any walk-in type enclosure with a floor area not more than 1sq.m provided its content is minimal risk, or floor area not more than 0.5sq.m if it contain electrical or communication equipment.
•  The spaces under raised floor with a height of 250mm or less.
•  The spaces above drop ceiling with a height of 1 m or less without combustible materials.
•  Concealed spaces under the roof with a height of 1 m or less without combustible material.
•  Covered paths: balconies, open-sided covered walkways & staircases, overlapping roof areas verandas, provided they are not used for storage of goods.
•  The area under structures such as platforms, ducts, and the like, within a protected room with 3m in width, provided the free flow of air reaching the detectors not obstructed.

Design requirement

•  For buildings or facilities with a total floor area of 8,000sq.m or less, a conventional system, semi-addressable system, or addressable system shall be used.
•  For buildings or facilities with a total floor area of more than 8,000sq.m, a semi-addressable system or addressable system shall be used.

Conventional fire alarm system

Legend: FACP-fire alarm control panel, HL-horn strobe, F-manual pull switch, S/H-smoke/heat detector

Difference between semi-addressable and addressable fire alarm system
Both types of alarm link devices (such as call points and smoke 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.

Who’s qualified to do this Job?
The FDAS system designer shall have the following qualification (based on RA9292);

• A registered PECE.
•  Experienced in the proper design, application, installation, and testing of FDAS as certified by IECEP.

PD 1096, the National Building Code of the Philippines

3. LEGAL COMPLIANCE
3.1 Section 301 of the NBCP provides that “NO PERSON, FIRM OR CORPORATION, INCLUDING ANY AGENCY, OR INSTRUMENTALITY, OF THE GOVERNMENT SHALL ERECT, CONSTRUCT, ALTER, REPAIR, MOVE, CONVERT OR DEMOLISH ANY BUILDING OR STRUCTURE OR CAUSE THE SAME TO BE DONE WITHOUT FIRST OBTAINING A BUILDING PERMIT THEREFORE FROM THE BUILDING OFFICIAL ASSIGNED IN THE PLACE WHERE THE SUBJECT BUILDING IS LOCATED OR THE BUILDING WORK IS TO BE DONE.” The NBCP also specifies the documentary requirements to be submitted as well as the general processes that local governments have to follow in approving the building permit application.

3.2 Section 309 of the NBCP provides that “NO BUILDING OR STRUCTURE SHALL BE USED OR OCCUPIED AND NO CHANGE IN THE EXISTING USE OR OCCUPANCY CLASSIFICATION OF A BUILDING OR STRUCTURE OR PORTION THEREOF SHALL BE MADE UNTIL THE BUILDING OFFICIAL HAS ISSUED A CERTIFICATES OF OCCUPANCY THEREFOR AS PROVIDED…”

Rule lll, Section 301. Building Permits

2.a. Ancillary Permits
The Ancillary permits duly signed and sealed by the corresponding professionals and the plans and specifications shall be submitted together with duly notarized application for Building Permit. THE BUILDING PERMIT IS NULL AND VOID IF NOT ACCOMPANIED BY THE ANCILLARY PERMITS. xxx.

Everything that involves to fire detection and alarm systems are contained in Electronics Engineering Law of 2004, or Republic Act 9292 - Section 5, a, b, and c.

While going back home after the presentation I overheard from passer-by that two commercial buildings near our city plaza caught fire and it was a bad sight passing that street going home. This is the reason why we need not having a second thought to implement crucial laws for safety. Unfortunately provincial areas do not strictly enforce laws on building code.

The fire detection and alarm system where meant to save lives and protect the properties.