Exactly where the ductwork leaves the compartment from which it serves (revealed in blue) it ought to maintain integrity and insulation fire ratings for a similar stretch of time as the compartment through which it passes. Promat has formulated self-supporting programs with out a steel liner, for instance PROMATECT®-Advertisement, PROMATECT®-L500 https://greasetightextractductwor35667.wssblogs.com/36808991/grease-tight-extract-ductwork-secrets