Joints of duct methods shall be created significantly airtight by the use of tapes, mastics, liquid sealants, gasketing or other approved closure devices. Closure units made use of with rigid fibrous glass ducts shall comply with UL181A and shall be marked181A-P for pressure-delicate tape, 181A-M for mastic or 181 A-H https://pipatembaga96306.tblogz.com/glasscloth-insulation-for-dummies-48711355