System Sensor BS5839 manual Location and Spacing of Automatic Fire Detectors, Ceiling Height

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2.4.LOCATION AND SPACING OF AUTOMATIC FIRE DETECTORS

It is important to consult applicable local and national standards when choosing the spacing and location of fire detectors. The following information is intended only as a guide to the location and spacing of detectors. There is currently no European standard available; hence this guide is based on BS5839 part 1, 2002.

2.4.1.Location and Spacing of Point Fire Detectors on Flat Ceilings

On a flat ceiling with no obstructions, the radius of protection of fire detectors is 7.5m for a smoke detector and 5.3m for a heat detector, and detectors should be mounted a minimum of 0.5m from a wall. Some analogue multi-criteria detectors have a heat sensor only function, switched by the control panel, typically used to reduce the possibility of false alarms during daytime when a building is occupied, reverting to multi- sensor operation at night time. If this type of operation is employed, the radius of protection for a heat sensor should be used. Figure 2.4.1 gives a simple spacing plan based on these figures, however it should be noted that this might not be the most efficient layout for a given site; for example in larger areas, it is also possible to use a staggered layout, see figure 2.4.2, which may reduce the number of detectors required. In practice, the layout of the room must be considered to obtain the most efficient detector layout.

 

.3m

.5m

5

 

7

 

 

 

 

 

 

 

 

 

7.5m

 

 

3.7m

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5.3m

 

 

10.5m

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Standard Smoke Detector Spacing

Standard Heat Detector

 

 

 

 

 

 

 

 

Spacing

 

 

 

Figure 2.4.1: Simple spacing plans for smoke and heat

detectors

13m

11.25m

60 °

60 °

Figure 2.4.2: Alternate smoke detector spacing plan for

protecting large areas

2.4.2.Ceiling Height

Smoke or heat detectors can only detect fires once a certain amount of smoke or heat has reached the sensor. As the height of a ceiling increases, the time taken for smoke or heat to reach a sensor will increase, and it will become diluted with clean, cool air. As a result, maximum ceiling heights are limited as indicated in table 2.4.1 below.

Detector type

Maximum ceiling height

 

 

Point smoke detector conforming

 

to EN54–7

10.5m

 

 

Heat detector conforming to

 

EN54–5 Class A1 (threshold 58°C)

9m

 

 

High temperature heat detector

 

conforming to EN54–5 Class B

 

(threshold 78°C)

6m

 

 

Optical beam detectors

25m

 

 

Table 2.4.1: Maximum ceiling height for different types of

detector

Often, a boundary layer can form close to the ceiling, which is free of smoke and remains cool. To avoid this, and maximise the probability of detection, smoke detectors should normally be mounted with their smoke entry 25mm-600mm below the ceiling, and heat detectors should be mounted with their heat element 25mm-150mm below the ceiling. Detector design normally ensures that the minimum requirement is met,

but care needs to be taken if the detectors are to be stood away from the roof, for example mounting on an open lattice suspended ceiling.

Another problem that should be considered is the possibility of stratification of the air in a room into hot and cold layers, causing the smoke or heat to stop at the boundaries. This particularly affects high rooms or atria, where beam detectors are often used. Stratification is very difficult to predict,

and can vary, even within the same room as environmental conditions change.

2.4.3.Ceiling Obstructions

Ceiling obstructions such as beams greater than 10% of the ceiling height should be treated as a wall, and will thus divide a room. Detectors should not be mounted within 500mm of such an obstruction.

If the depth an obstruction such as a beam is less than 10% of the height of the ceiling, but greater than 250mm deep, then detectors should not be mounted any closer than 500mm to the obstruction.

Where an obstruction such as a beam or a light fitting is less than 250mm in depth, detectors should not be mounted any closer to the obstruction than twice its depth (see figure 2.4.3 below)

Where a ceiling comprises a series of small cells, for example a honeycomb ceiling, or a series of closely spaced beams, for example floor of ceiling joists, the recommended spacing and siting of detectors changes further, dependant on the ceiling height and the depth and spacing of the beams. Reference should be made to relevant standards for details (in the UK BS5839 Part 1: 2002, 22.3.k Tables 1 and 2).

Application Guide

Note: This document is based on the recommendations of BS5839 Part 1: 2002. It is intended only as a guide to the application of fire detection systems.

Reference must be made to relevant national and local standards.

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Contents Guide to intelligent fire systems Contents Guide to Intelligent Fire Alarm SystemsGuide to Intelligent Fire Alarm Systems Intelligent Fire Alarm Systems Alarm SystemsIntelligent Fire System Fault Tolerance Decimal address switchesAddressing Methods Dedicated address programmerPRE-ALARM Facility Intelligent Fire Alarm SystemsFire System Zones Remote Leds Programming of Intelligent Fire Alarm PanelsInterface Modules Advantages of Intelligent SystemsDetector Application Guide GuideFire System Categories Category M SystemsApplication Guide 1. Manual Call Point Positioning Manual Call PointsSelection of Automatic Fire Detectors Rate of rise heat detector Fixed temperature detector 58CAreas subject to rapid changes During normal useCeiling Height Location and Spacing of Automatic Fire DetectorsDetector type To EN54-7 10.5m Heat detector conforming toCorridor being 7.5m and 5.3m respectively CorridorsSloping Ceilings Location and Spacing of Optical Beam Detectors Lantern LightsVoids and False Ceilings Visual Alarm Signals Audible Alarm SignalsCodes and standards in the UK BS5839 Part 12002, Section Maintenance of Fire DetectorsGeneral Specifications Series 200 Plus FeaturesIntelligent Product Range Series 200 Plus Analogue Addressable Detector RangeSystem Sensor Intelligent Product Range Weight2251EM Photoelectric Smoke Sensor 2251TEM PHOTO-THERMAL Sensor5251REM, 5251EM and 5251HTEM Heat Sensors Drift Compensation and Smoothing6500S Beam Detector Remote Test SwitchWeight 142g Operating Temperature -10C to 55CLaser Detector 2251EIS Intrinsically Safe Detector and IST200 Interface With LED blink enabledB500 Series Bases Interior diameter Weight 100gExterior diameter DepthM200XE Short Circuit Isolator Module M200 Series Module RangeM201E Output Module Specifications Max Standby Current, externally powered zone5A at 250VAC M210E-CZ Conventional Zone ModuleCall Points AccessoriesIndoor Indoor products are generally rated at IP24DDetector Base Sounders Audio Visual ProductsSounder Strobes Majority of back box formatsOther Information Approval Bodies for Fire Detection Products Other InformationAvenue Hoch Paris, France Tel +33 1 53 89 00 Jernholmen DK-2650 Hvidovre Denmark Tel +45 36 349Volochaevskaya Str 40, Bld System Sensor Fire DetectorsTelephone + 7 095 Telephone + 91 124 Fax + 7 095

BS5839 specifications

System Sensor BS5839 is a standard that pertains to fire detection and alarm systems, providing guidelines for the design, installation, and maintenance of these essential safety tools. It is crucial for safeguarding lives and property, ensuring that fire detection systems are effective and reliable. The BS5839 standard, established in the UK, covers a wide range of fire alarm system types, including conventional, addressable, and wireless systems.

One of the main features of BS5839 is its comprehensive classification of fire detection systems. The standard divides systems into categories based on the level of risk and the environment in which the system will operate. This classification helps ensure that the system installed meets the specific needs of the building and its occupants. For example, Category L systems are meant for life safety, while Category P systems are designed to protect property.

The technologies underpinning BS5839 include various types of detectors, alarm devices, and control panels. Smoke detectors, heat detectors, and multi-sensor detectors are prominent among the devices specified in the standard. Smoke detectors use photoelectric or ionization principles to detect smoke and signal an alarm, while heat detectors respond to temperature changes. Multi-sensor detectors combine both smoke and heat detection technologies to provide a more reliable response to fire conditions.

Another key characteristic of BS5839 is the emphasis on regular testing and maintenance. The standard outlines procedures to ensure that systems remain operational and effective over time. This includes routine system checks, functional testing, and more in-depth inspections at regular intervals. Ensuring that systems are maintained according to BS5839 is vital for compliance with insurance requirements and for safeguarding against potential legal liabilities.

Furthermore, BS5839 highlights the importance of staff training and awareness. It emphasizes that personnel responsible for fire safety must be adequately trained in the operation and response to fire alarm systems. This ensures that in the event of a fire, occupants are prompted to take appropriate action and evacuate safely.

In summary, System Sensor BS5839 provides a crucial framework for fire detection and alarm systems. Its classification of systems, incorporation of advanced technologies, and emphasis on maintenance all contribute to enhanced safety and compliance, protecting lives and property effectively.
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