Enclosed ___-type luminaires shall be installed in ducts or plenum chambers used to transport environmental air when illumination is necessary for maintenance and repair.

• A. screw
• B. plug
• C. gasketed
• D. neon

Answer: (C)

In ducts or plenums that move environmental air, luminaires must be designed to stay sealed and protect the interior from the moving air. An enclosed and gasketed luminaire provides a tight seal, preventing air leakage, moisture, and dust from entering the luminaire and also keeping any heat or sparks contained. This reduces the risk of airflow-related problems and keeps maintenance lighting safe and effective in the air-handling environment. The gasketed enclosure is what makes a luminaire appropriate for these spaces, whereas non-enclosed or non-gasketed types aren’t built to withstand that environment. Neon lighting isn’t suitable for this maintenance context, and “screw” or “plug” types don’t inherently guarantee the necessary enclosure and seal.