ELI5: Why does fresh air feel better to breathe in than indoor air?

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The lungs are evolved to be good at sensing two things: Co2, and a lack of Co2. Fresh air feels more fresh because it has a bigger lack of Co2 compared to your average indoor building. The brain is also capable of connecting “cold” to fresh. Hence why, for instance, cold water generally tastes more fresh than warm water. When the air is too hot, it can feel suffocating, even if you’re outdoors. In the northern hemisphere, for the most part, ‘outside’ is going to have a higher combination of ‘lack of Co2’ and ‘colder than inside’ to trigger a ‘this is fresh air’ feeling in your brain

Excludos

May depend on a lot of stuff but it mostly comes down to CO2. We humans need to take O2 into our bodies and kick the CO2 away. Too much CO2 suffocates humans. As the time passes, humans inside consume the limited O2 indoors and increase the CO2. Our bodies detect the difference and start sending signals to our brains to either open the window/door/whatever or leave the room, just to protect the body from suffocating.

kutzyanutzoff

I’ve always thought it was weird that when you come in from outside in the spring and you have your windows open it smells fresher than the outside WHICH IS IMPOSSIBLE.

dalekaup

Indoor air pollution. Chemicals from fragrances, VOC’s, etc build up indoors. These chemicals are toxic and are known to cause migraines, loss of concentration, fatigue, etc. 25% of women and 10% of men experience office migraines. The likely discrepancy is likely due to the fact that women are much more likely to wear products containing fragrances which cause their headaches. Men are least likely to wear them which likely explains why they experience less office headaches than women, simply because they aren’t as exposed to those chemicals.

lkso

Because it contains more fresh ingridients and less CO2, unlike the indoor air that is being breathed in constantly and therefore overused and therefore not fresh anymore. Outside air constantly gets “replaced”, so to say.

DoctorofEngineering