Buildings

Space Heaters 2

by Arnie Katz

Q:  In Arnie Katz's article in your June issue he states 'Ventless heaters or fireplaces should never be used in homes.' Is this opinion or fact? I have a ventless fireplace and would like to know. Why would they make ventless heaters if they are not safe for homes? Please try to clear this up.

A: Thanks for your excellent question. The statement you quote is my opinion. Below is what it's based on.

Whenever you burn gas— natural gas or propane—by-products of the combustion process are created. If the burner is well-tuned and clean, the primary by-products are:

• Carbon dioxide (CO2) - not considered a direct health risk for people exposed to it
• Water vapor - not only benign but is actually necessary for life
• Nitrogen oxides - lung irritants, but typically aren't produced in large amounts

So far, so good.

My concerns are centered on two primary issues:

1. Production of carbon monoxide (CO) under certain circumstances
2. Negative effects from pumping a lot of water vapor into the air of your house

Let's look at the CO issue first. The Consumer Products Safety Commission reports that up to around 1980, there were approximately 70 deaths a year caused by unvented heaters. At that time, a safety device was added to shut off heaters if oxygen levels at the burner got low enough to produce substantial amounts of CO. I believe this has helped considerably and have not seen evidence of deaths from the newer types of heaters.

I have, however, seen—and measured—significant levels of CO in rooms with unvented heaters and fireplaces. This is widely reported by many professionals in the building performance industry who routinely measure CO in houses.

While these heaters typically burn very cleanly when new, they don't burn quite so cleanly after carpet fibers, pet hair and dust accumulate on the burners over time. The owner's manuals say the units should be serviced annually by a professional to clean the burners; however, I've never met anyone who actually has that done.

The other issue of concern is the water pumped into the air. As my grandmother used to say, "Too much of anything, even a good thing, is no good." Here's a scenario I've seen a number of times: People on a tight budget close off much of the house and spend the winter in one or two rooms heated by a ventless heater. The water vapor generated by the heater goes to the coldest part of the house, where it condenses on walls. The wet walls promote mold growth, and soon we have large amounts of mold in the house.

I'm not one of those people who panics over every little mold spot. We are, after all, in North Carolina, where mold is everywhere. But walls covered with mold can present a significant health hazard, especially if someone in the home has asthma, allergies or other respiratory problems. This is just not a good idea.

Finally, I've read the owner's manuals for a number of different brands of unvented heaters and fireplaces. Every one of them said you should always open a window when using the heater. That is, the window is the vent and you are living in the chimney. Ventless heaters and fireplaces are promoted as being 99 percent efficient. What happens to the efficiency when you open the window?

Each of the manuals also stated that these heaters should not be used in rooms where there are people with certain medical conditions, such as heart disease, respiratory illness, pregnancy, asthma, allergies, etc.

For me, the only reasonable conclusion is that these devices should not be used in spaces where there are people with the medical condition called "being alive."