Country Life

In 12 of the 13 experimental tests, the doors did not “meet the acceptance criteria” to pass the rigorous fire test, regardless of gap size; only a double set of steel doors with a three-quarters-of-an-inch gap were able to meet the criteria to pass both tests required in NFPA 252, Standard Methods of Fire Tests of Door Assemblies. The tests generally showed that larger gaps increase airflow, which seemed to make it more difficult for doors to meet the acceptance criteria to pass, the report’s authors noted.