Why do not we breathe equally out of each nostrils?

When you get near a mirror and breathe out by means of your nostril, the mirror will fog up. Two marks of water vapor will pool on the floor, one for every nostril. However one mark shall be bigger than the opposite, as a result of folks breathe largely out of 1 nostril at a time.

So why will we not often breathe out of each nostrils directly?

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