Before After
External portions only account for about 25-30% of the exhaust system, so a thorough inspection must be of the entire exhaust system, beyond the hood and into the duct work and fans.Duct work is crucial to carrying those vapors out of the cooking area, although in the event of a fire, the duct should be able to contain the fire and prevent the flames from escaping into the building.

Remember that the ideal situation is to have a clear view of the fan blades that help carry the vapors away. If you can only see steel and grease, that may be the sign of a serious problem.

The duct and fan should be checked roughly every six to 12 months, depending on your insurance policy requirements.