Modern Solutions Inc.

 The un-vented gas range above was the chief cause of excessive moisture on the windows of a home I recently inspected. It was also a contributing factor in the mold growing on the windows, doors and walls. I have seen un-vented gas ranges as the sole cause of mold in other homes as well. Although the mold outbreak was the motivation for my client’s call, and mold should always be taken seriously, the mold was not my immediate concern.

Having sensed a problem after taking my first breath of air in the house, and then seeing the un-vented range and the moisture on the windows, I promptly did an oxygen test in the home. I discovered that the ambient oxygen level had been reduced from 20.9% down to a startling 19.3%. This is 1.6% lower than the oxygen level found in outdoor air.

This drop may not sound like much, but keep in mind that in order for oxygen levels to go down, nitrogen-the other key ingredient in our air-must also go down at the same rate. Being that there is an approximate 4 to 1 ratio of nitrogen to oxygen, if the oxygen drops by 1.6%, then the nitrogen would have to drop by 6.4%, leaving a total drop of 8% for both gasses. The missing 8% must then be replaced with other gasses in the air. In short, it would take approximately 80,000 PPM of other unhealthy gasses to cause an oxygen drop of just 1.6%. This is double jeopardy: something essential to healthy air is taken away and something bad replaces it.

We are supposed to breathe 20.9% oxygen in our air to be healthy. This is what nature produces for us outdoors. In an average home environment the oxygen levels will commonly be between 0.5% and 1.0% lower than the outdoor air, even without having a gas range in the kitchen.

To better understand the severity of this problem, if the oxygen level drops by just 1% in a commercial building, OSHA can shut down the building and evacuate it for safety reasons. Of course, this is under the assumption that someone is actually paying attention to the air in the building.

People who work in underground mines or other confined spaces must wear safety gas alarms that will sound off for evacuation at the hazard level of 19.5%.

A home is neither a commercial building nor a regulated workplace, and therefore not monitored, meaning that no one is paying attention to unsafe oxygen levels inside residential properties. Personally, I find it scary when I see these conditions in homes, especially those where children are present or in senior housing where people on fixed incomes are trying to save every energy dollar by never opening their windows.

I have become suspicious that poor air quality, particularly indoor environments with low oxygen levels, is a leading cause for Attention Deficit Disorder (ADD) in both children and adults, as well as Alzheimer’s disease. I surmised this due to the fact that one of the first things to go in a poor indoor air quality environment is the ability to think clearly or remember things. I have seen other research beginning to look into the relationship between the skyrocketing rates of ADD in children and depleted oxygen levels in indoor air. I am certain as this research continues it will further validate my suspicions.

Just imagine the short- and long-term health effects that can be attributed to living in a home with your family and pets breathing the same oxygen deprived air over and over, day after day, month after month. How good would you expect your memory to be? How energetic would you expect to feel when you get up in the morning? How alert would you expect to be at work the next day? How well would you expect your children to perform when trying to study at school?

Un-vented gas ranges only serve to make this entire problem much worse. I have heard the myth that the gas ranges today are much more efficient, produce less carbon monoxide, and therefore have no need to be vented to the exterior. Though exterior venting may not be required by code yet, this is a myth nonetheless. The truth is that every gas range should be vented directly to the outdoors and that the range hood vents should be used diligently, even if only one burner is being used.

You may recall from science class how quickly just one tiny candle flame can devour the oxygen out of just one gallon of air. Now extrapolate that into the number of flames on just one gas range burner and multiply that by how long that burner is fired during cooking. Then, figure in the possibility that more than one burner is being used, or a gas oven was being used as well. Consider how quickly the oxygen reservoir can be depleted from the interior of a new, air-tight, energy-efficient home, or a home that has had energy-saving measures performed on it to make it more air tight. It is bad enough that we have families and pets that can quickly use up the limited amount of oxygen in air-tight homes, but add an un-vented gas range and it is a sure recipe for dangerously depleted oxygen levels.

Furthermore, old gas ranges can produce up to 800 PPM of carbon monoxide. Newer ranges may be slightly more efficient, but compare them to a furnace that only produces 15 PPM and is still mandated to be vented to the outdoors. A heating contractor would fall over if he saw a furnace venting to the indoors, but little or no thought is given to the effect a gas range can have on indoor air quality.

There are three key detriments of gas ranges that are not vented to the exterior; all three can cause illness.
1. They produce immense amounts of moisture indoors which can cause and/or contribute to mold contamination in homes.

2. They produce low levels of carbon monoxide, not enough to set off a CO alarm, but enough to contribute to ill health due to time-weighted average exposure.

3. They rapidly burn up the indoor oxygen supply, reducing oxygen levels to those unsafe for humans and pets.

In the house I mentioned above, the wife and two toddlers were still home, but the husband-a large oxygen consumer-was already gone for several hours. The doors had been opened numerous times throughout the morning prior to my arrival at 11:00 a.m. Yet, the oxygen level had risen to only 19.3%, which is still below evacuation standards.

In addition to the excessive moisture and mold growth, I could only imagine how bad the oxygen levels were in that home earlier that same morning. The family of four had been consuming oxygen since the evening before, plus the range had been used to cook both dinner and then breakfast before a door was even opened. I would guess that the oxygen levels could have been as low as 18%. Keep in mind that at sustained levels of 16.5% we can die from asphyxiation. In fact, there are more deaths from oxygen deficiency than from any other type of gas.

Not only should all gas ranges be vented directly to the outdoors, but it is just as critical that every home have a make-up air vent installed. If a make-up air vent is already present, it should be inspected to see if it has an inline barometric or spring-loaded damper. If so, it should be removed or propped open permanently. Because air travels the path of least resistance, removing or circumventing the damper is the only way to assure functional oxygen replacement.

If you have a gas range, and it is properly vented to the outdoors, the exhaust fan should be used every time the range is turned on. This will eliminate the excessive moisture from the house and carbon monoxide poison from the air, as well as help pull in an equal amount of essential fresh air through the make-up air vent.

So as not to cause confusion, an air-tight, energy-efficient home is a good thing. However, we must be very mindful as to how quickly the indoor air can go rancid if we do not take the necessary safety precautions. Technically, there are six different strategies required to protect indoor air and having a proper way for fresh air to get back into a home is one of them.

While I plan on doing more research into the residential oxygen problem, in the meantime, I feel obligated to extend a warning about what appears to be common sense, but is still a much overlooked health concern.

Please be sure to read the articles titled “Make-up Air Ventilation” and “Just Open Your Windows.”

 by Building Inspector and Indoor Air Specialist, Dan Schilling
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