Exhaust ductwork simply provides the way to transfer smoke, contaminated air, grease vapors and odors from the hood to the fan. Ductwork needs to be in compliance with building codes and also should be conducted of at least 16 gage or 18 gage stainless steel. If possible they should be routed vertically to the roof of the building with minimal turns to reduce the loss of pressure. Combustible grease accumulates overtime if the ducts are not cleaned periodically. Without proper maintenence, dangerous grease levels may result in health hazards (from the growth of bacteria and mold) and kitchen fires, not to mention decreased productivity from the fans.

Duct is wrappedd in fire blanket insulation when run through combustbile materials such as wood rafters. This is required by the mechanical code.

Again, grease build up is a huge safety hazard in the restaurant business. It is the leading cause of fires in a commercial kitchen so it is crucial that grease filters are replaced and changed weekly or monthly, depending on the amount of pollution that goes through.