Type I ventilation hoods are required to be installed above cooking equipment that produce grease or smoke. They are specifically designed to remove condensation, heat, smoke, and grease and oil-laden vapors produced by cooking. They are commonly referred to as grease hoods and it is required for these hood ducts to be fully welded. The main benefit to using these types of hoods is that a bank of grease baffle hood filters helps to contain grease and other contaminants before they enter the rest of your exhaust duct system. This keeps your ducts and upblast exhaust fan cleaner between servicing and maintenance.