HVAC Journeyman Practice Exam

Where should smoke detectors be installed as part of an automatic shutoff system?

1. Return air duct ahead of any fresh-air inlet

2. Main supply air duct served by such equipment

3. Fresh-air inlet

4. Main return and the main supply duct

The correct answer is: Main supply air duct served by such equipment

Installing smoke detectors in the main supply air duct served by the HVAC equipment is essential for effective monitoring of smoke presence within the system. This placement allows the detectors to sense smoke that may be generated by a fire within the ducting or from connected spaces. Since the supply duct is responsible for distributing conditioned air throughout the building, having smoke detection here means any smoke detected can trigger an automatic shutoff mechanism, helping to prevent the spread of smoke and potential fire hazards into occupied spaces. This strategic location ensures that potential threats are caught early on, enhancing the overall safety of the HVAC system and the building it serves. Detecting smoke in the main supply duct helps facilitate an immediate response to a fire situation, allowing for faster evacuation and mitigation efforts. Other placements may not be as effective; for example, positioning detectors in the return air duct or fresh-air inlet may not provide the same level of early detection, as these areas could be further from a fire source and may not have direct exposure to smoke generated within the building. Therefore, the main supply air duct is the most effective and logical choice for smoke detection in an automatic shutoff system.