In the absence of this change the default would be for the materials to be noncombustible, which was never the
intent. The technical committee clearly noticed that because its committee statement on comment 90A-33 was
“The committee concludes that this is a material that would default to the general material requirements”.
However, as pointed out by both Dwayne Sloan and myself, the default, if this language is not incorporated into
the standard, is that materials that are not specifically mentioned must be noncombustible. At present NFPA
90A sends the user to a section that refers to the ASTM E 84/UL 723 requirements (4.3.3) but it applies only to
“supplementary materials for air distribution systems”.