For Christmas my wife gave me a Netatmo weather station because I am a home weather station nerd. The Netatmo is very cool, but it has an unexpected feature: it measures indoor Carbon Dioxide (CO2) levels. As soon as I set it up, the Netatmo began to alert that our indoor CO2 was at an unsafe level. The notes said that outdoor CO2 is usually around 400 ppm, and numbers above 1500 ppm could be unhealthy. On that first day, my house was at around 1300 ppm. Prior to that, I never gave indoor CO2 levels a thought. I began to do some research and discovered high levels of CO2 can cause symptoms such as fatigue, headache, breathing difficulties, strained eyes and itchy skin. My family does have all of these issues, especially on the weekends when we are home all day, but I never connected that to indoor air quality.
Previously, I installed a Nest thermostat. The Nest is very smart and saves energy by learning your habits and programming itself. Unfortunately, it is so efficient, that the HVAC fan is frequently off - and not pulling in fresh air. The previous, programmable thermostat also limited the HVAC use. The original, 1960's era thermostat was dead simple and had an option to just turn on the house fan and leave it on.
The solution to keeping the fancy, smart Thermostat, saving energy, and not gassing the family, turns out to be free and not too complicated. Go to the Website called "If This Then That (IFTTT)," set up a free account, enable your Netatmo connection and your Nest connection, and then turn on the fan recipe that I published. That's it. The recipe watches the Netatmo device, and if the CO2 levels go over 750 ppm, then it tells your Nest thermostat to turn on the fan for 15 min. I chose 750 ppm arbitrarily, so feel free to change it - or make your own recipe. The Netatmo chart, below, shows the CO2 levels in my house for the last week. IFTTT keeps logs, too, so you can see every time the recipe is triggered. Since I set this up, I have not had a headache on the weekend. Of course, your mileage may vary.