Exhaust-fan installation key to minimizing fire risk
Tim Carter
Q: I'm excited about remodeling my kitchen, and I would appreciate your advice about choosing an exhaust fan.
I'm hearing conflicting information from contractors, the kitchen designer and my husband. Can you address the “best practices” for kitchen exhaust fans and any other aspects to ensure the safety of my family and my house?
A: All you have to do is talk with a few seasoned firefighters to understand why it's so important to pay attention to detail when installing kitchen exhaust fans.
Many a restaurant has burned to the ground because of an exhaustsystem fire that turned the vent pipe into a roaring jet engine.
When you cook greasy foods, the grease can vaporize much like water does when it is boiled. The hot grease vapor touches exhaust-fan filters, fan blades, ductwork, cabinets, the ceiling and other surfaces in your kitchen. It then condenses on those surfaces. Soon, there's a layer of grease that is flammable.
If you ever have a fire in the exhaust ductwork, you want it to stay there.
This is just one reason that you want a powerful kitchen exhaust fan — so you can blow as much of this grease vapor outdoors before it has a chance to coat anything.
The first step is to buy a top-quality exhaust fan that's appropriately sized A kitchen exhaust fan can pose a fire hazard, and improper installation increases the chances of a damaging blaze. for the square footage of your kitchen. Read the installation instructions to understand the exact height of the fan over your cooktop for maximum performance.
The instructions will also tell you the size, type and length of the solid-metal
pipe or duct you must use between the fan housing and the exhaust hood on the exterior of your home.
Be aware that bends in the pipe restrict flow. A 90-degree bend, for example, usually equals 10 feet of straight pipe with regard to friction.
Do not terminate the exhaust pipe in an attic or crawlspace. The exhaust must exit your home through a sidewall or out through your roof.
Do not put the exhaust termination pipe under a soffit where the greasy vapor can enter soffit vents and get into your attic.
All joints where pieces of metal pipe or duct connect must be taped with a special metal tape. You can buy aluminum or even stainlesssteel tape that adheres well to the metal pipe. If there's a fire in the duct, the tape prevents the fire from spreading to combustible things near the pipe.