Air Handler Smoke Detectors and the NFPAAir Handler Smoke Detectors NFPA - Installing duct smoke detectors or smoke detectors in air handlers are not ideal for the protection of life and property in the event of a fire or smoke condition. The NFPA and mechanical codes cover smoke detectors.

Air Handler Smoke Detectors NFPA

It is preferred that the occupied and non-occupied areas and spaces have smoke detectors simply because the fans in air handlers or that move air through ductwork may not be operational at all times so having smoke detectors in the ductwork will not offer the amount of protection that smoke detectors would offer in the spaces or area served whether those areas or spaces are occupied or not.

Yes, if the fan is operational it would create a negative at the return and suck the smoke into the ductwork where a smoke detector would trip and alarm people there was smoke in the building somewhere but ideally, in most circumstances, it is better to have smoke detectors in the spaces and areas of the building for better protection.

Air Handler Smoke Detectors NFPA | Purpose

Smoke detectors are ideal for detecting a problem with the air handler. For example, if the fan motor were to begin smoking the duct detector would, ideally, shut down the system before the fan caught on fire. Furthermore, the NFPA specifically states that detectors installed in the air duct system shall not be used as a substitute for open-air protection.

So, now that we know the NFPA states smoke detectors in the ductwork are no substitute for open-air smoke detectors protection is there a requirement for smoke detectors in the ductwork? Yes, whenever the air capacity in the ductwork or air handler exceeds 2000 CFM’s the smoke detector needs to be installed in the ductwork or handler downstream of air filters and upstream of any branch ducts. The purpose is not to spread smoke throughout the building with the HVAC system. As you can imagine, smoke is deadly and you don’t want the ductwork being used to spread it throughout the building.

Safety Interlocks Wiring

The system should have hard-wired safety interlocks that trip fan control in the event of smoke detection. This means if smoke were detected power would be cut to the relay/contactor controlling the fan motor. This should be applicable to air handlers that include multiple fans or a single fan motor. Again, always check with the immediate Authority Having Jurisdiction (AHJ) for their requirements for smoke detection and control.

Air Handler Smoke Detectors NFPA | Code Authorities

The codes are constantly changing so it’s good to stay updated. The NFPA changes the code based on changes by ANSI, UL, the industry, and events that occur where safety is improved. However, each distinct AHJ follows the code that satisfies its requirements. If you want things to go smoothly when inspection time arrives, take the time to check with the AHJ to ensure the job is done to the AHJ’s requirements. If you disagree with AHJ, bring the dispute up with them beforehand. It will save you time and money in the long run.

Always check with the local code authorities before making a decision about where to install smoke detectors in an air handler or ductwork. Some local codes will require a duct detector installed in the return and the supply while others are not so stringent. There are also exceptions to the NFPA for smoke detectors installed in duct air systems. Exhaust fan systems do not require smoke detectors, however, again always check with local codes as these normally supersede national codes such as the NFPA.

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Air Handler Smoke Detectors and the NFPA