Duct Detector Sampling Tube Requirements

Dst1 5 2 to 4 ft.

Duct detector sampling tube requirements. The sampling tube should be angled at least 1 4 downward for every 12 of duct width per figure 4. Air is introduced to the duct smoke detector s sensing chamber through a sampling tube that ext ends into the hvac duct and is directed back into the ventilation system through an exhaust tube. Dst10 2 piece must extend a minimum of 2 3 the duct width. Usually installers provide sampling holes on a two foot grid in two directions over the face of the grille to meet this requirement.

The holes must be facing into the air flow see figure 2. The intake sampling tube consists of a piece of steel piping with a series of holes drilled the entire length of the tube and should extend the entire width of the duct. Standard location when factory mounted will be on the side opposite the damper actuator. The physical location of the detector in each room should ensure the detector is readily accessible to view the smoke conditions in the room and for easy servicing.

The intake sampling tube consists of a piece of steel piping with a series of holes drilled the entire length of the tube and should extend the entire width of the duct. In multi story buildings at each story with a commonly shared return and having a capacity greater than 15 000 cfm s. The equivalent duct diameter for a rectangular duct is the diameter of a circle that results in the same area as the rectangle. Outside duct width sampling tube recommended up to 1 ft.

Dst1 5 2 to 4 ft. Duct detectors smoke detection nfpa 90a code requirements in air supply systems with a capacity greater than 2000 cfm s downstream of the air filters and upstream of any branch ducts. The sampling tubes may be ordered to a desired length or ordered in one of 3 standard lengths and cut per requirements. Dst5 8 to 12 ft.

Dst3 4 to 8 ft. Dst10 2 piece must extend a minimum of 2 3 the duct width. If there are more than 2 holes in the section of the tube extending out of the duct select a shorter tube using table 1. Sampling tubes recommended for different duct widths.

Outside duct width sampling tube recommended up to 1 ft. If the detector is. These sampling tubes can only be used with new innovairflex duct smoke detectors. There should be 10 to 12 holes spaced as evenly as possible across the width of the duct.

Prior to the installation of the damper and smoke detector. The sampling tubes may be ordered to a desired length or ordered in one of 3 standard lengths and cut per requirements. The inlet sampling tube is to be located between blades to avoid blockage of the airflow past the tube. Nfpa 72 recommends but does not require that duct smoke detectors be located in a duct section that is between 6 and 10 equivalent duct diameters from bends or openings.

These sampling tubes can only be used with new innovairflex duct smoke detectors. Dst3 4 to 8 ft. Dst5 8 to 12 ft. For proper air sampling duct pressure should be a minimum of 0 01 inches of water.

Sampling tubes recommended for different duct widths. Dst1 1 to 2 ft.