Which action is associated with opposing off a purlin?

• A. Louvers a 4'x8' panel on joists
• B. Smoke indicator made on fire side of operational area before cutting is initiated
• C. Smoke indicator made on the fire side after cutting
• D. Install a panel on a joist

Answer: (A)

When you’re dealing with opposing off a purlin, the objective is to create a controlled, removable vent opening without compromising the roof’s main support. Louversing a 4'x8' panel on the joists achieves this best: it gives you a large, ready-to-use vent surface that can be opened or closed quickly, and it’s supported by the joists so the purlin itself isn’t weakened. This setup allows you to manipulate the opening as conditions change while keeping structural integrity, which is the essence of opposing off a purlin.

The other options don’t accomplish that same goal. Smoke indicators placed on the fire side relate to detecting when to act, not to creating the vent opening. Installing a panel on a joist is related but doesn’t specify the removable, louvers-style approach that directly supports opposing off a purlin.