1. The fact that the humidity is often too low where I am at. I got a humidifier. Before using this thing I had dry nostrils, but never paid attention to it. No

1. The fact that the humidity is often too low where I am at. I got a humidifier. Before using this thing I had dry nostrils, but never paid attention to it. Now it’s better. 2. The way cooking affects pm2.5. I don’t have great ventilation in the kitchen, so I started ventilating via windows for a better air quality at home. I do not feel effects of this though. 3. How fast the CO2 levels are rising with closed windows. Since my childhood it was regular in my family to sleep with windows closed, and ventilate maybe couple of times per day. And in the summer time the windows were closed when the air was cooled with a conditioner. It turns out, that in an hour with closed windows the CO2 level is already higher than what is considered healthy. Nowadays it seems like I can say when room needs ventilation without a sensor, just cause I feel the air is not "nutritious" enough. I do feel worse (tired, slight headache) when not ventilating.