Which of the following statements about sealing fittings is true?

The statement that it must be at least the metric designator is accurate because sealing fittings are designed specifically to prevent the entry of gas or dust into enclosures in hazardous locations. This requirement ensures that the fitting maintains its integrity and meets the appropriate standards for safety and performance. The metric designator refers to the minimum specified size that the sealing fitting must adhere to in order to effectively perform its function. By ensuring the sealing fitting meets or exceeds this designator, it reduces the risk of hazardous materials infiltrating the electrical enclosures, thereby enhancing safety in potentially explosive environments.

The other statements may not align with the recognized standards for sealing fittings; for instance, fittings must meet certain criteria to be effective and safe, which includes the requirement for their size and listing. It’s important for such fittings to be compliant with regulatory standards to maintain a safe operating environment.