In Class I, Division 1 locations, the conduit to a splice box must be sealed if the trade size is which of the following?

• A. 1 inch or larger
• B. 2 inches or larger
• C. 2 1/2 inches or larger
• D. 3 inches or larger

Answer: (B)

In hazardous Class I, Division 1 locations, you must block any path for flammable vapors to migrate into a splice box through the conduit. When the conduit entering the splice box is 2 inches trade size or larger, a conduit seal is required to create a gas-tight barrier at that entry, preventing vapors from traveling along the conduit and potentially igniting inside the box. This threshold protects the enclosure integrity for larger conduits where the risk of vapor migration is greater. Smaller conduits do not require this seal under the same rule, so the seal is not mandated for those.