Q&A - Hidden Mold in Wall Cavities, Ventless Gas Fireplaces

by Thad Godish, Ph.D

Hidden Mold In Wall Cavities

Question:
What evidence is there to support the advice that all mold in wall cavities must be remediated? Is there scientific data that shows how many or how few mold spores are released into the room from a wall cavity behind an otherwise normally-painted wall?
- Janet , California

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Answer:
Actually the evidence that has been presented at scientific meetings so far is quite mixed. In one reported case such "hidden mold" was associated with mold levels elevated above normal. In a second case it was not.

Whether "hidden mold" is a problem that requires remediation depends on a variety of factors. These include the extent of the infestation, the likelihood that it will contribute to increased airborne mold levels, the likelihood of disturbance, and in what walls it is located.

"Hidden mold" in an external wall is a problem and should be remediated. External walls are subject to air infiltration through the wall due to pressure differences caused by the wind and by indoor/outdoor temperature differences. In houses with hidden mold in exterior walls, it is not uncommon to smell mold odor on breezy-to-windy days and smell mold odor coming out of electrical outlets on such external walls. There is no doubt( based on my own testing experience) that such hidden mold increases indoor mold levels and mold exposures. As such, remediation is strongly recommended.

Hidden mold is also common in interior walls and floor cavities. These are typically associated with plumbing leaks and often involve gypsum board infestation by Stachybotrys. Is such "hidden mold" a problem? Intuitively, it is probable that in most cases it is not. Once the cavity is opened and not quickly resealed, it is more probable that an exposure risk will develop.

From a mold remediator's standpoint, it is good practice to remediate all mold, including that which is visible and that which is not. If one doesn't, and sometime in the future "hidden mold" is exposed, one will be held liable.

Editor's Note: See the Mold Center for more information about mold remediation at AllergyBuyersClub.com

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Ventless Fireplaces

Question:
My husband and I and my daughter are living in a house that is approximately 2500 sq.ft. We have a ventless gas fireplace in our bedroom and one in our living room. Just recently, my husband lit the pilot lights of the fireplaces and ran them. The entire house smells of an awful odor, which my husband says it's just because the fireplaces have never been lit before and it's just burning off the new smell and the dust. We've had them off and on for the last week, but the smell is still around. My 6-year-old daughter complained of the smell in her bedroom this morning. Today I had a bad headache, but I get them every once in a while, so I'm not sure if it's from the fireplaces or not. I've printed out literature on the effects that these ventless gas fireplaces can cause, but my husband says that I'm crazy and that he's going to use the fireplaces. I'm mainly concerned for my daughter's health and safety and it doesn't seem to bother him.
-Carla, Florida

Answer:
The odor is likely to be due at the least initially to the newness of these systems. As such, it should decrease with time. If it doesn't, there is a problem with them and they should not be used.

I don't recommend ventless fireplaces as they emit a variety of potentially health-affecting contaminants into the air of one's home. These include carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), aldehydes and lots of water vapor. Though water vapor is not directly harmful, its condensation on building surfaces can contribute to the development of mold infestations which on exposure to airborne mold spores can cause significant problems.

A ventless fireplace in a bedroom is an especially poor idea absent some way to move air around the house, it can result in very high local concentrations of the contaminants described above.

The amount of CO produced by such devices depends on how well they are tuned, how long they are operated, and how small the space where they are being used. If you want to check on the CO level, I recommend the use of a digital Nighthawk CO detector capable of recording the maximum concentration (retrieved by pushing the button). The merits of these devices were described on a previous posting (check archives on the IEN website). The CO level should not exceed 5 ppm. If it is over 15 ppm, there should be an increased level of concern and may cause headaches in a sensitive person.

Children are at special risk of exposure to airborne contaminants since they receive a higher dose because of their smaller body mass. I especially don't recommend the use of ventless fireplaces in houses where young children are present.

Your husband's response is a classical case of denial. Wishing such devices to be safe does not make them so. The use of ventless fireplaces almost under any circumstances is a "poor idea."

December 19, 2002
Indoor Environmental Quality (2000) Thad Godish, Ph.D, C.I.H.

Reprinted with permission.

Editor's Note: See all air purifiers at AllergyBuyersClub.com

First Published: March 2003
Updated: September 2003

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