Fire Detector Placement Chapter 14 Page 425

Objectives Describe how detectors are listed by Underwriters Laboratories (UL) Explain why detectors are not permitted to be positioned too close to the corners of a room where the ceiling meets the wall Determine the spacing of detectors in a room with a smooth flat ceiling Determine locations of detectors in a room with unusually configured walls

Objectives Space detectors in a corridor Discuss rules for placement of detectors on sloped ceilings Determine the locations of detectors on ceilings with solid joists or beams Explain why detectors are not permitted to be located too close to supply air ducts

Objectives Describe the effect of floor-mounted partitions on a ceiling jet Determine the optimum locations for beam detectors, flame detectors, gas detectors, and duct detectors

Heat Detector Listings Heat detectors are listed by UL as follows: Heat detector type Temperature rating Listed smooth ceiling spacing between detectors Listed smooth ceiling spacing to wall or partition Contact arrangement Detector model number

Smoke Detector Listings Smoke detectors are listed by UL under category UROX as follows: APPLICATION DETECTOR TYPE COMPATIBILITY RESTRICTIONS INSTALLATION CRITERIA

Spot-Type Detector Spacing Corner Placement for Spot-Type Detectors: The 4-Inch Rule Smooth Ceiling Spacing of Spot-Type Detectors Spot-Type Detector Spacing for Unusual Wall Configurations Spot-Type Detector Spacing in Corridors

Spot-Type Detector Spacing Figure 14-1. Ceiling jet dynamics for corner fires; NFPA 72 prohibits spot detectors being placed within the “blind spot”

Spot-Type Detector Spacing Figure 14-5. Illustration of .7 Smax rule, or “circle of coverage”

Ex. 14-1: Ceiling Spacing of Spot-Type Detectors

Ex. 14-2: Ceiling Spacing of Spot-Type Detectors – Spacing Less than Listed Spacing

Ex. 14-2: Ceiling Spacing of Spot-Type Detectors – Spacing Less than Listed Spacing

Ex. 14-2: Ceiling Spacing of Spot-Type Detectors – Spacing Less than Listed Spacing

Spot-Type Detector Spacing Spot-Type Detector Spacing for Smooth Peaked Ceilings Spot-Type Detector Spacing for Smooth Shed Ceilings Spot-Type Detector Spacing for Solid Joist Construction

Spot-Type Detector Spacing Figure 14-8. Sectional view of a peaked ceiling; a detector must be placed within 3 feet (900 mm) of the roof peak, and spacing is measured along the floor, not along the slope

Spot-Type Heat Detector Spacing for Beamed Construction Body Of NFPA 72 Spot-Type Heat Detector Spacing for Beamed Construction—Annex of NFPA 72 NFPA 72 requirements Effect of Ceiling Height on Spot-Type Heat Detectors

Ex. 14-3: Detector Placement for Beamed Construction

Ex. 14-3: Detector Placement for Beamed Construction

Spacing Of Line-Type Heat Detectors Spacing requirements (see Table 14-1, Page 441): Line-type detectors on a ceiling must be not more than 20 inches from the ceiling Line-type detectors are mounted to the bottom of solid joists Line-type detectors are mounted to the bottoms of beams, where beams are less than 12 inches deep and less than 8 feet apart on center

Spot-Type Smoke Detector Spacing Spacing near Air Vents Spacing near Floor-Mounted Partitions Spot-Type Smoke Detection for Raised Floors and Suspended Ceilings Spot-Type Smoke Detectors in High Air Movement Areas Spot-Type Smoke Detectors for Smoke Control Systems

Spot-Type Smoke Detector Spacing P.443 Figure 14-13. Smoke detector spacing for beamed construction

Projected Beam Smoke Detector Spacing P.451 Beam detectors work on the following principles: Beam detector consists of sender and receiver NFPA 72 (2007) requires that The sender and receiver be mounted firmly to avoid movement of the projected beam and possible unwanted alarms The projected beam remain unobstructed by storage, ceiling-mounted equipment, or other objects that would result in a trouble condition on the FACU and prohibit the detectors from sensing smoke

Projected Beam Smoke Detector Spacing Smoke obscures the projected beam and reduces transmission of the infrared beam to the receiver Beam detectors are for indoor use, and are to be mounted to stable surfaces Mirrors can be used with projected beams, per manufacturer’s instructions, provided that mirrors are mounted to stable surfaces

Projected Beam Smoke Detector Spacing Spacing for smooth ceilings must be per manufacturer’s instructions For beamed construction, some manufacturers require that beam detectors be mounted in each beam pocket if Beam depth exceeds 18 inches Support beam spacing is greater than 8 feet

Projected Beam Smoke Detector Spacing For solid joists less than 8 inches in depth, some manufacturers require that the ceiling be considered as a smooth ceiling NFPA 72 requires beam detectors on sloped ceilings be installed parallel to peak

Projected Beam Smoke Detector Spacing Figure 14-23. Sloped ceiling installation for beam detectors

Flame Detector Placement A flame detector can perceive a fire that is viewed within its cone of vision Its ability to sense a fire depends on Position of the fire within the cone of vision Distance from the fire to the detector Size of the fire Matching the spectral response of the detector to the spectral emissions of the fire

Flame Detector Placement Each flame detector is listed for a specific viewing angle that defines the cone of vision Placement of flame detectors usually requires considerable field experience and consultation with the manufacturer

Gas-Sensing Detector Placement May sense a potentially hazardous condition in advance of ignition, or may sense gaseous combustion by products Spaced in accordance with NFPA 72 (2007) and their listing NFPA 72 has replaced detailed spacing requirements on gas-sensing fire detectors

An Engineering Approach To Heat Detector Placement Best way to ensure detection in a building Conduct fire testing in numerous areas Determine best detector Determine best detector locations Calculated Heat Detector Placement per NFPA 72 Annex B (2007 Edition)

Summary The placement of detectors must consider Type of fire Dynamics of the ceiling jet Attributes of the detector Properties of the ceiling or surface onto which the detectors are mounted NFPA 72 provides minimum requirements for the spacing of detectors

Summary Designers must analyze the anticipated fire and the space requiring detection Annex B of NFPA 72 provides engineered approach to positioning detectors Specific requirements for Heat detectors Smoke detectors Beam detectors Gas detectors