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Positioning of Smoke and Heat Detectors 

All smoke detectors have similar spacing requirements, heat detectors also all have similar 

spacing requirements although these are different to smoke detectors. According to BS5839

for general areas the spacing between any point in a protected area and the detector nearest to

that point should not exceed 7.5m for a smoke detector and 5.3m for a heat detector.

The above are the maximum areas that can be covered by an individual detector. In order to

ensure that coverage is provided into the corners of rooms and to ensure that there is no gapat the junction point of multiple detectors, spacings have to be reduced.

To ensure complete coverage for square layouts, spacings between detectors and walls should

 be reduced to 5m for a smoke detector and 3.5m for a heat detector.

To ensure complete coverage, spacings between detectors should be reduced to 10.0m

 between smoke detectors and 7.0m between heat detectors

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For corridors less than 2m wide only the centre line need be considered therefore it is not

necessary to reduce detector spacings in order to provide complete coverage. Therefore for 

smoke detectors spacing becomes 7.5m from a wall and 15.0m between detectors. For heat

detectors the spacing becomes 5.3m to a wall and 10.6m between detectors.

The above data is based on flat level ceilings; for pitched ceilings or ceilings with a non-flat

surface, spacings will alter. For pitched ceilings use the data below, for other ceiling types

refer to BS5839 for comprehensive guidance. Where detectors must be mounted onto a

 pitched ceiling, a detector should be mounted near to the apex but spacing can be increased by 1% for each 1° of slope up to 25%. ‘Near’ is defined as within 600mm for smoke

detectors and within 150mm for heat detectors.