CO2 Too Now?

Previously I posted about finding natural gas leaks in four out of six homes I checked using a natural gas detector, including my own.

Next up, I decided to check for “Sick Building Syndrome” in a few homes, including my own. I was a little surprised by by findings.

Sick building syndrome is typically caused by poor ventilation that allows for a buildup of gasses, chemicals, CO2, mold, etc. that can cause people to feel some range between a-bit-off to terribly sick. One method of determining if a building does not have adequate ventilation is to check carbon dioxide levels, abbreviated as CO2. High levels of CO2 means there obviously isn’t enough ventilation to refresh the air in relationship to the air that’s being burned or exhaled.

Now, don’t confuse CO2 with CO, which is carbon monoxide. Checking for CO is common because CO in high doses is a quick death. CO detectors are sold along side fire detectors.

CO2 is different. We breathe out CO2 with each breath. Plants absorb the stuff. Our outside air, as of this point in human civilization, generally has around 350-400 ppm (parts per million) of CO2. We breathe it all day long. Thus, it is not in itself a hazard in normal quantities. Yet, government recommendations are that office buildings should remain below 1000 ppm. Apparently studies show that a level of just 1000 ppm of carbon dioxide will reduce the ability to concentrate by about 30 %. It takes more massive concentrations, above 15% (150,000 ppm ), to cause immediate unconsciousness, so there’s apparently a large range between feeling off and medical crisis.

I originally picked up a CO2 Monitor out of pure curiosity about our air quality after finding natural gas leaks in our house. The device sits in a room and monitors CO2, humidity, and temperature. We just had a new high efficiency furnace installed, so I really wasn’t expecting to find an issue. Surprise.

Plugged the monitor in. Our levels were above 800 ppm. I had no idea if that was normal. Searching the internet was confusing. Higher levels, over 1000 ppm, were listed as a problem in office buildings, but there was little info out there on what is considered normal in a house. Occasionally the alarm on the monitor would sound, alerting me to the fact that our levels were suddenly over 1000 ppm. Interesting. What could cause that? I admit to having gadget fun. I played with it for days off and on doing various tests. I tested different rooms. I tested near different appliances. I cracked open windows. Turned on and off the furnace fan. What I finally realized was that when the furnace was running the CO2 in our house would steadily rise, about 1 ppm per second. Was this normal? Heat the house a degree or two hotter and we’d jump well over 1000 ppm setting off the alarm. If I opened windows the levels would drop down to around 400 ppm.

Right away I decided to leave the windows upstairs open a little at all times. I also turned the furnace fan on continuously to keep the air circulating and mixed. This seemed to help keep the levels down to around 850 ppm, as long as I didn’t change the temperature on the thermostat. I erased the programmed temperature changes so the furnace wouldn’t cool the house at night, because in the morning the CO2 levels would set off the alarm.

On Thanksgiving I took the device over to my parents house. It clocking in well above 1500 ppm! I realized it was due to their gas stove and oven being on all day long. They didn’t have a vent in the kitchen to refresh the air, so they were breathing in the CO2 produced by continuous open flames. Perhaps it wasn’t just the Turkey making us sleepy. A follow up test conducted on another day found their levels between 800 and 900.

Took the monitor to another house. There the living room was in the 500s, but when we placing it in a closed bedroom that was host to a sick person, the levels were way up above 1000. In this case it was due to a lack of air circulation. The bedroom door had been closed all day and night with someone breathing out CO2 to fill the small room. Essentially, the air was stale. I suggested the owner of the house turn the furnace fan on to help circulate the air, but they were too worried about burning out the motor if it ran day and night, so they cracked open a window instead. The nights are well below freezing, but I recall when I was young, before heating costs were one of my concerns, I preferred to sleep with the window open as well during the winter. I liked the fresh air.

You can install a whole house heat exchanger to avoid losing as much heat and cold when pulling air into the house from outside, but apparently you need to maintain these just as you do your furnace air filters and humidifier, and so they are not suggested by HVAC installers very often.

Well, unable to determine if the high numbers on our house were normal, I decided to call the company that installed our furnace. They sent two guys out to inspect my concerns. At first they said it might just be normal operation, as no one had ever asked about CO2 before. Just the same, while they were there they set about making some minor adjustments.

They asked if we insulated the walls and had done any other efficiency changes to the house recently. A well insulated house leaks less air and is more likely to have CO2 buildup. We have done very little. Our walls are actually hollow. I started researching spray-in insulation over the summer, but have yet to do it.

While here they adjusted the slope of the exhaust. Modern efficient furnaces have their own fresh air intake and exhaust out pipes. Ours was sagging in the middle, and the slope was very slight. Second, they added a U to one of the water drainage pipes that came off the air intake. I also asked them to change the furnace to run the fan motor at a slower speed when the fan was used continuously. That would allow more efficient, silent, slow and steady air circulation.

After they left I found the CO2 levels had dropped dramatically. Unoccupied rooms on the first floor were in the 400s. The average level I now get in my office while working is just under 550, and the maximum I’ve seen for occupied rooms on the first floor has been around 650. The CO2 levels no longer climb when the furnace is running. When I checked, I found that in the middle of the night the levels actually dropped below 400 in my office. Yeah, our house is not sealed tight, so that was outdoor late night air quality. That’s a leaky house. Maybe I do need some more insulation in my walls.

The second floor levels still rise a bit at night, getting into the 700s. I know why. We have no cold air return upstairs, so the air isn’t circulating. Getting a return air duct upstairs is now on my to-do list.

So, once again, my curiosity and love of gadgets proved very interesting, this time pointing out that we needed to get the furnace corrected.


No comments yet. Why don’t you start the discussion?

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.