Overview; Special Considerations; Special Considerations For Smoke Detectors And Sensors; Smoke Detector And Sensor Applications - Simplex 4098 Manual

2 Overview

This document provides information about the correct application of both heat and smoke detectors/sensors in conjunction with fire
alarm systems.
The information in this publication is intended to be used as a technical guide only. Ensure that the requirements of applicable codes and
standards, as well as the directives of Authorities Having Jurisdiction (AHJs) are followed.
2.1

Special considerations

Before installing detectors or sensors, make a survey of the area to be covered in accordance with the information provided in NFPA 72, an
excerpt of this is provided in Smoke detector and sensor
Proper Use of System Smoke Detectors.
2.1.1

Special considerations for smoke detectors and sensors

Consider the following before installing detectors or sensors:
• Is there human occupancy?
• The contents to be protected.
• The type of construction and use.
• The burning characteristics of contents.
• The air movement - stratification.
• The deflections and obstructions.
• The height of ceilings.
• The surface conditions of ceilings.
• The type of ceiling construction.
• The total area.
• The vent locations: velocities and dilution.
2.1.2

Smoke detector and sensor applications

Each detector/sensor can provide up to 900 square feet, or 84 square meters of coverage, depending on the following:
• The requirements of local codes.
• The results of engineering evaluation.
2.2

Where to place detectors and sensors

2.2.1

Correct locations for detectors and sensors

Important: The guidelines in this section are adapted from standards published by the National Fire Protection Association, Quincy,
Massachusetts, U.S.A. These standards include NFPA 72, "National Fire Alarm and Signaling Code"; NFPA 70, "National Electrical Code", Article
760; and NFPA 90A, "Standard for the Installation of Air Conditioning and Ventilating Systems."
To provide effective early warning of a developing fire situation, install smoke detectors or sensors in all areas of the protected premises.
Total coverage as defined by NFPA 72 includes all rooms, halls, storage areas, basements, attics, lofts, and spaces above suspended
ceilings including plenum areas utilized as part of the HVAC system. In addition, this includes all closets, elevator shafts, enclosed stairways,
dumbwaiter shafts, chutes, and other subdivisions and accessible spaces.
Fire detection systems installed to meet local codes or ordinances may not be adequate for early warning of the fire. Some codes or
ordinances have minimum objectives, such as capturing elevators, or preventing circulation of smoke through HVAC systems instead of
early detection of fire.
Weigh the costs against the benefits of installing a complete fire detection system when any detection system is being installed. The
location, quantity, and zoning of detectors or sensors is determined by the objectives of the installation, rather than the minimum
requirements of any local codes or ordinances.
Detectors or sensors can be omitted from combustible blind spaces when any of the following conditions prevail:
• Where the ceiling is attached directly to the underside of the supporting beams of a combustible roof or floor deck.
• Where the concealed space is entirely filled with noncombustible insulation. In solid joist construction, the insulation need only fill the
space from the ceiling to the bottom edge of the joist of the roof or floor deck.
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4098 Detectors, Sensors, and Bases Application Manual
applications. For additional information, refer to NFPA 72 and the NEMA Guide for
574-709 Rev. AP