Where in an HVAC system is a backdraft damper installed?

A backdraft damper is specifically designed to prevent unwanted air from flowing back into a space or ductwork when the system is not actively exhausting air. Its primary function is to allow air to flow in one direction while blocking it from reversing, which is particularly important in exhaust systems to prevent contaminants, odors, or harmful gases from re-entering living spaces.

In the context of the options provided, installing a backdraft damper in ducts used for bathroom and residential kitchen hood exhaust is essential because these areas typically generate exhaust air that must be expelled from the home. The backdraft damper ensures that when the exhaust system is off, outside air does not flow back through the duct and into the home, maintaining indoor air quality and preventing drafts.

The other scenarios mentioned do not typically require a backdraft damper to function correctly. For instance, while a damper could be involved in supply or return ducting scenarios, they do not face the same backflow risk posed by exhaust applications. The primary purpose of a backdraft damper aligns with managing exhaust airflow effectively, making the installation in exhaust ducts critical for maintaining the intended operation of HVAC systems in kitchens and bathrooms.