California IDEX Practice Exam 2026 – Comprehensive Test Prep

The use of fire-rated dividers is an effective method for preventing the horizontal spread of fire within a plenum. Fire-rated dividers function by creating barriers that can withstand heat and flames for a specified duration, thus controlling the movement of fire and smoke. They are essential in compartmentalizing spaces and providing more opportunities for occupants to evacuate safely while minimizing damage to property.

Increasing ventilation could potentially exacerbate a fire by supplying it with more oxygen, which is not a desirable action when trying to contain a fire. Smoke detectors are crucial for early detection but do not actively prevent the spread of fire. Water sprinklers can help with fire suppression but may not effectively stop a fire from spreading horizontally before it is detected or controlled. Therefore, using fire-rated dividers is the most appropriate choice for preventing the horizontal spread of fire within a plenum.