Today I was teaching a Certified Indoor Environmentalist course in Connecticut when we measured carbon dioxide (CO2) levels in the meeting room. When I read 2,850 parts per million (ppm) on my meter, I immediately assumed something was wrong with the device. That was upsetting because it had just come back from factory calibration. In such a well conditioned, modern meeting room, we couldn’t really have CO2 levels that high, could we? A typical meeting room ranges from say 800-1,200 ppm.
When taking the device outdoors, we were getting readings around 380 ppm as one would expect (see chart). In other areas of the hotel, levels were more in line with expectations (around 1,000 ppm). Our high levels were not a computer glitch, but an accurate reading of the CO2 levels in the space.
Here is a key point learned by the class today: ventilation may be lacking even in a room that feels cool & crisp and is well maintained. It’s not just hot and stuffy rooms that may be under-ventilated. This reiterates the importance of measuring ventilation either directly or approximating it with the use of a surrogate such as CO2.
In a future blog post I’ll describe the advantages and disadvantages of using CO2 to approximate ventilation. It’s a good screening tool that incorporates mechanical and natural ventilation (not to mention air infiltration as well).