Did a post get deleted? I did not see any post as to the legality of the filters. Legality is not determined by NFPA, UL or UL-C. Legality is determined by a goverment agency. A government agency may adopt a standard as law, or it may notor may adopt parts of a standard. (Oregon has done that ) If a government agency does adopt a standard as law, any subsequent revision may or may not be adopted as law. To further compoind the confusion, other model codes, such as International Building Codes may also refer to other codes, referencing them as standards. IBC references NFPA 10, which refers to NFPA 96. However, IBC does not direclty reference NFPA 96. Instead, IBC has a different set of codes for exhaust systems which are not a strict or thorough as NFPA 96. Aluminum filters do not meet NFPA standards, but are still sold.
When refering to legality of certain supplies or job processes, be carefull. What is law in one area of jurisdiction, may not be law in another jurisdiction. For instance in California, NFPA 96 is law, or soon will be because California has adopted NFPA 5000, a model buildng code. I do not know when NFPA 5000 is to go into effect. And now, because of the new Gov, that decision may be recinded and the IBC may be legislated into law.
Douglas Hicks
General Fire Equipment Co of Eastern Oregon, Inc