Duct smoke detectors are allowed to have tubes protruding into the air duct to sample the air stream.

Duct smoke detectors are allowed to have tubes protruding into the air duct to sample the air stream.

• A. True
• B. False
• C. Not sure
• D. Not applicable

Answer: (A)

Duct smoke detectors can use a small sampling tube that protrudes into the duct to draw air to the sensing element. This arrangement is common and allowed because it lets the detector monitor the air inside the duct while keeping the sensing components accessible or located outside the duct. Proper installation follows manufacturer instructions and NFPA 72: use a suitably small sampling tube, place the sampling point in a representative, straight portion of the duct away from sharp bends or diffusers, protect the tube ends, and ensure the installation doesn’t cause excessive pressure drop or airflow disturbances. In short, protruding sampling tubes are an accepted, standard method for duct smoke detection.

Duct smoke detectors can use a small sampling tube that protrudes into the duct to draw air to the sensing element. This arrangement is common and allowed because it lets the detector monitor the air inside the duct while keeping the sensing components accessible or located outside the duct. Proper installation follows manufacturer instructions and NFPA 72: use a suitably small sampling tube, place the sampling point in a representative, straight portion of the duct away from sharp bends or diffusers, protect the tube ends, and ensure the installation doesn’t cause excessive pressure drop or airflow disturbances. In short, protruding sampling tubes are an accepted, standard method for duct smoke detection.