Published Monday February 9, 2015

Indoor CO2 (carbon dioxide) Meter
(Not to be confused with a CO or carbon-monoxide meter).

For well over 150 years we have known that CO2 is a greenhouse gas and excess levels of it will warm the Earth. To see this process in action, check out your local elementary school for a science demonstration that uses 2 identical, clear bottles, 2 thermostats, some dry-ice and a couple of incandescent lights. 

CO2 levels over the past 800,000 years. 

Earth's atmospheric C02 levels have slowly varied naturally throughout the ice ages. Only recently, in the last 150 years have CO2 levels started an unnatural progression quickly upward. As long as global CO2 levels remain below 350 ppm, global warming will not be a problem and climate as we know it will remain the same. Unfortunately, we smashed the 350 ppm mark back in the 1980's and are now breaking 400 ppm, a level not seen in Earth's atmosphere in perhaps 8 million years. Like it or not, through our fossil fuel burning ways, humanity is drastically altering the Earth's climate. 

CO2 levels over the past 50 years. Can you see the Earth breathing?

CO2 as an Indoor Pollutant

While measuring and tracking global CO2 levels is a good indicator of climate change and anthropogenic global warming, measuring CO2 levels inside the home is also an indicator of air quality and good ventilation inside the home. 

For as little as $129, you can buy your own CO2 Meter. 
Click on the link below. 

A typical CO2 reading of 768 ppm (parts per million) inside our home. 

A home will have more air exchanges with the outside air when the temperature difference between the inside and outside is greater. Cold air outside (greater temperature difference), will cause the most air leakage/exchange. When it's windy outside, air is also exchanged more quickly.

In a home that does not have enough ventilation, VOCs, (volatile organic compounds) and other pollutants can increase and reach unhealthy/dangerous levels. 

CO2 is an easily identifiable and measurable gas. While high CO2 levels are not necessarily a bad thing for occupants living inside a home, when CO2 levels are high, that is a rough indicator that VOCs and other pollutants, (that are harmful to us) are also at elevated and dangerous levels. 
Foul smells are also an indicator of pollutants in the house. 

Very high levels of CO2 inside a plastic bag after breathing in a few breathes. 
I should get an O2 meter now. Since 10,000 ppm of CO2 is only 1% and normal air is around 20% oxygen, there is probably a lot more oxygen still in the bag than CO2, but breathing this much CO2 for a long time would still be dangerous. 

Typical CO2 levels at Church:

Sometimes I get sleepy at church and I wondered if the reason was simply not enough ventilation?  So during an especially crowded sacrament meeting, (it was the ever-popular primary program), I took some readings. The overflow in the back of the chapel was open and full of people but all the doors were closed. 

Sacrament Meeting CO2 levels (11/2014 chapel doors closed)

 Time ppm CO2 Notes
 11:00 am 752 as sacrament meeting started.
  1500 During the sacrament
  1700-1832 primary program
  1975 1/2 way through
 11:54 am 2000 
 12:08 pm 2020 
 12:13 pm 2077 end of meeting
  2097 socializing afterwards

OK, so I'm a nerd and I just got this CO2 meter! Can you blame me? Maybe because it was the primary program but I didn't get sleepy this time. Levels were elevated but not alarmingly so. Ventilation is sufficient.
Now let's go into the very crowded Relief Society room for Sunday school. 

Sunday School (a packed room with the doors closed).

 Time ppm CO2 Notes
 12:22 pm 1520 Start of class, (another class just got out)
 12:30 pm 1900 Took readings at every 100 ppm increase
 12:33 pm 2000 CO2 rising 100 ppm every 3 minutes. 
 12:36 pm 2100 CO2 rising 100 ppm every 3 minutes. 
 12:40 pm 2200 CO2 rising 100 ppm every 4 minutes. 
 12:44 pm 2300 CO2 rising 100 ppm every 4 minutes. 
 12:52 pm 2380 CO2 levels still rising but slower now. 
 12:55 pm 2400 CO2 levels still rising but slower now. 
 13:02 pm 2480 CO2 levels appear to have peaked. 
 12:05 pm 2420 Class is over

CO2 levels were higher but still, not alarmingly so, considering ~100 people were in the small classroom, I'd say the ventilation system was working sufficiently well. 

CO2 Levels in the house:
I spent a lot of effort air sealing our home but am concerned that perhaps it is now too air tight. A long-term indoor CO2 level of more than 1000-1500 ppm is considered un-healthy, (not from CO2 itself but due to other pollutant levels that could also be elevated). I was relieved to find that rarely does our house CO2 levels exceed 1000 ppm. Only during very mild days do the CO2 levels climb much higher than that and it is during these times we might open the windows anyway. 

Seasonal CO2 levels inside the home

 Date Time ppm CO2 Notes
09/15/201410:251036 Mild outside tempratures
09/15/201410:49 999 Reading taken on floor vent
09/15/201411:43 293Reading taken in concrete, underground room under porch. Air supply probably comes from the dirt. The last time global CO2 levels on earth were at 293 ppm was in the year 1900. 
11/12/2014 05:54 768 26 F outside and 10 mph winds. 
01/10/201511:06  581 
01/23/201506:18 490 
02/09/201510:10 675 

Operating an indoor clothes dryer pulls air from the house, increasing your HVAC bills. In homes that are poorly ventilated, it may also serve to ventilate the old stale air and cause fresh outdoor air to be drafted inside. During the seasons when the attic air is hotter than the temperature inside the house, our clothes dryer does not draft air from inside the house.