What's your reaction if you hear that indoor CO2 levels are at 1000 parts per million (ppm)? If you're not involved in indoor air quality (IAQ), probably not much. But consider this: 1.5% of the air you breathe could be air that someone else just exhaled. That means every five minutes, you might be taking in a lungful of someone else's breath.

Sounds unsettling, right?

But it gets more concerning. In places like crowded meeting rooms, CO2 levels can soar to 2000 ppm. This means you could be breathing in over 4% rebreathed air! It’s not surprising then that higher levels of CO2 are linked to an increase in sick days.

While CO2 ppm figures might not initially grab your attention, translating them into the percentage of rebreathed air can dramatically change your perspective.

For those eager to dive deeper, plenty of studies and articles delve into this issue. David Elfstrom has even created a spreadsheet that charts indoor CO2 levels against the amount of rebreathed air (you can find the link in the comments).

Now, let's turn this into a conversation: What are the CO2 levels in your environment, and how do you feel knowing about the rebreathed air percentage?

Jasmeet Singh
Author