Tonight as we went to bed my partner asked if I wanted the fan turned off. I replied if it wasn't bothering her I preferred it on. It was easier for me to breath. I have COPD and yes it is my own stupid fault. I had never thought about it analytically before but being among other things a biochemist I have this theory. When we breath we breath in oxygen and breath out CO2. If motionless in a room where the air is still causes a concentration gradient of increasing CO2 and decreasing oxygen around the sleeper. This is solved by moving the air or tossing and turning.