Which statement about supply air is true?

• A. It Is Never Filtered Or Conditioned
• B. It Is Generally Filtered, Fan-Forced, And Either Heated, Cooled, Humidified, Or Dehumidified As Necessary
• C. It Is Only Outdoor Air
• D. It Is Always Unconditioned

Answer: (B)

The main idea is that supply air is the air delivered to the occupied space after being treated by the HVAC system. It is generally filtered to remove particulates, moved by a fan (fan-forced) to push it through the ducts, and conditioned to meet space requirements—meaning it can be heated or cooled and humidity adjusted (humidified or dehumidified) as needed for comfort and IAQ. Outdoor air is often mixed with return air, but supply air itself isn’t restricted to being outdoor air; it is the conditioned air that actually enters the space. The other statements are incorrect because supply air is indeed filtered and conditioned, it isn’t limited to outdoor air, and it isn’t always unconditioned.