In Japan, the building code requires every room to have an air vent [1]. Initially I was skeptical of them and was looking to close them to save on heating cost

In Japan, the building code requires every room to have an air vent [1]. Initially I was skeptical of them and was looking to close them to save on heating costs in the winter. But after doing a little research, I decided they are probably best left open to reduce condensation and mold growth. Now I'm curious how effective they are at keeping down CO2 levels at night. I would like to try this experiment in my house. [1] https://resources.realestate.co.jp/living/japanese-apartment-air-vents-use/ https://resources.realestate.co.jp/living/japanese-apartment...