A colorless, odorless gas at room temperature, carbon dioxide (CO2) is an abundant substance. It can be a liquid or a solid known as dry ice. Normal cell function produces carbon dioxide. When humans breathe out, carbon dioxide is expelled. Dying plants and burning fossil fuels produce carbon dioxide. All houses have a presence of carbon dioxide, with certain causes creating high levels.
The soil underneath a house contains carbon dioxide from decaying plants and animals. If the soil was used in farming, it contains fertilizers, manure and other nutrients applied to the soil to increase productivity. Many times farm land is converted into housing developments. When that occurs, the high levels of carbon dioxide can enter the house. The process involves the CO2 gas being drawn out of the soil into the house. The difference in air pressure between the house and the soil causes the house to suck up the carbon dioxide gas from the soil into the home.
Lack of Fresh Air
Carbon dioxide builds up in a house, whether from the gas being drawn up from the soil or from the activities of humans and pets. Unless the indoor air is circulated on a regular basis, high levels of carbon dioxide will appear. Levels tend to be higher in the areas of the house where the occupants and pets spend most of their time. An indication that the levels are getting higher would be accelerated activity by plants who thrive on carbon dioxide.
According to PropEx.com, certain appliances in a house can cause elevated levels of carbon dioxide. These include space heaters, dryers, stoves and any other unvented gas appliance. One way to prevent the buildup is to make sure all appliances are properly vented. The appliances should be regularly checked to ensure they are functioning properly. Carbon dioxide detectors are available for home use and would be another way to verify that your appliances are not causing a problem.
An improper heating, ventilation and air conditioning system (HVAC) can lead to high levels of carbon dioxide. Many homes rely totally on the system to recirculate air; the windows are never opened to let in fresh air. A maintenance call for the system would be one of the first indications it's a cause of high carbon dioxide. Symptoms of high CO2 include headaches, dizziness, difficulty breathing, fatigue and increased heart rate. Basically, the high CO2 deprives the body of its needed oxygen, especially the brain.