Range hoods

to vent or not to vent
By Arnie Katz
Range hoods

(Photo courtesy of Broan)

Q: My brother, who tends to be a "know-it-all," was visiting and told me our range hood is the recirculation type, and that I need to replace it with one that vents to the outside. I never paid much attention to it, but since my son was diagnosed with asthma, I've been noticing range hoods wherever I go and asking my friends what they have. Most people I know have the recirculation kind, and they seem to work fine. Is this really a problem?

A: Range hoods have several purposes. The recirculation type does only one thing: it collects grease from cooking and deposits it on the filter. This is a good and useful thing as long as you clean the filter. If you do a lot of frying, you'll need to clean the filter a lot more often than if you don't.

A vented range hood does several more things for you. Cooking and baking put "stuff" into the air in your house. What kind of stuff? Well, moisture, for one thing. A little extra moisture isn't necessarily a bad thing, particularly in the winter if your house tends to get very dry. But too much moisture can cause condensation on windows and walls and ceilings, which can lead to mold and mildew and, in extreme cases, rot. This usually takes a number of years to show up.

For most of us, a little mold or mildew is no big deal. After all, we live in North Carolina and are surrounded by a zillion kinds of mold every time we step outside. But for some of us, especially those with asthma, allergies and other respiratory problems, mold in the house can be a very big deal and can make us very sick.

In addition to moisture, baking can emit fine and ultra-fine particles of ash and other pollutants when the stuff that spilled in the oven burns — again, probably no big deal for most of us — but a real problem for some folks with compromised respiratory function. Small particle pollution has been linked to heart disease as well.

If you have a gas range, like I do, there are some other things to worry about. Whenever we burn anything, there are products of combustion. Natural gas and propane are relatively "clean" (compared to, say, the wood in your fireplace). If everything is working just right, mostly you'll get water vapor (more moisture) and carbon dioxide.

In the real world, however, after dust and grease and dog hair accumulate on the burners, or they get slightly out of adjustment, some other stuff like carbon monoxide and nitrogen oxides are given off. Bake a casserole for an hour, or let a pot of soup simmer for an afternoon, and the levels of these pollutants can be higher in your house than the government allows there to be in the air outside.

Unless you have a range hood vented to the outside. And it's working properly. And you use it.

There is not good research on how big a problem this is. Clearly, you and your neighbors aren't falling over dead because you have a non-vented range hood. But just as clearly, some folks are being made sick. If you can save one ER visit for an asthmatic child, or reduce the amount of medication he has to take, you can pay for the vented range hood very quickly.

In a rational world, your health insurance would pay for switching out the range hood. It would save the insurance company money, it would save you money, and your son would probably feel better. But I'm not holding my breath waiting for that one.

About the Author

Arnie Katz is the former building science consultant for Advanced Energy in Raleigh. advancedenergy.org

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