This year the OH Fire code is undergoing revisions to bring it up to the 2015 IFC requirements. In this process, there is a comment period in which anyone with interest can make comments on the proposed revisions or ask questions. One such question was asked about the revisions to
5704.2.7.3.2. Vent Line Flame Arresters and Pressure-Vacuum Vents
Is the intention to require flame arrestors or pressure-vacuum vents ONLY for Class 1B and Class 1C liquids? (emphasis added by me)