Smoker System Ductwork issues

During inspections in the past few years, there has been a disconcerting amount of type 2(or worse) ductwork use for wood fired smoker systems. These systems not only lack proper insulation and fire containment, but they have major issues with clearance to combustibles, leakage and complete failure of the ductwork with the systems actually splitting apart. We highly recommend installing welded ductwork or  Class 1 listed systems.  Many systems actually have round heating ductwork used to exhaust the flammable fumes and affluent. Please see pictures below on what many are not seeing above their smokers. It is very important to get clear pictures of the complete outside and inside of your smoker systems or even get a good look yourself. With the rash of  fires in these systems, it is extremely important to pay attention immediately. Your exhaust system cleaning company should be able to provide a complete report with pictures. Ask for this. Please see the pictures of one inspection showing all of these issues and why we cannot be using this type of ductwork for any exhaust system and what to look for.

                                          Above we see the ductwork completed rotted out 
                                                     and split apart above the ceiling

                                         Here we see there the  rotted ductwork has zero 
                           clearance where it passes through the wood roofing plywood.