Which option correctly states the size that triggers sealing for a conduit to a splice box in Class I, Division 1?

• A. 1/2 inch or larger
• B. 2 inches or larger
• C. 1 inch or larger
• D. 2 1/2 inches or larger

Answer: (B)

In Class I, Division 1 locations, sealing the conduit entry into a splice box is about stopping flame or gas from traveling through the conduit into or out of the box. When the conduit is large enough—specifically, two inches in diameter or larger—the potential energy and volume of gas that could be carried into the enclosure are greater, so a proper seal is required to prevent ignition from propagating along the conduit. That threshold is why the correct choice is two inches or larger. Smaller conduits don’t trigger the sealing requirement; with proper fittings, they’re considered adequately protected without an additional seal. Use of an approved sealing method for the larger conduits helps maintain the explosion-protection integrity of the enclosure.