🔍 Key Concepts

• Identify which dampers are labeled N.C. (Normally Closed) and which are N.O. (Normally Open) on the RA-0009 diagram. • Trace the pneumatic control line to see whether the three dampers share one pilot air signal or if there are separate signals feeding each damper. • Note the function of the recirculation/return air path versus the outside air and exhaust air paths in a single‑zone HVAC mixing box.

💭 Think About

• On loss of control air, which dampers would you want to fail closed to the weather and which would you expect to fail open to keep some air circulation? Relate this to the N.C./N.O. markings next to each damper. • Follow the small control-air line coming from the right side of the diagram: does it split to feed all three dampers from the same source, or does each damper get its own independent control device? • Compare the four answer choices: two are about which dampers are normally open/closed, and two are about how many pilot air signals there are. Use the diagram to eliminate at least one option from each pair.

✅ Before You Answer

• Verify from the symbols that the outside air and exhaust dampers each have an explicit N.C. or N.O. label; don’t assume based on typical practice. • Check whether there is a single pilot air line feeding a group of positive-positioning relays (P) for the dampers, or multiple separate pilot lines. • Confirm which damper in the recirculation/return path is marked N.O. or N.C., then match that combination exactly with the answer choices before deciding.