Are you a mouth breather? This is a question that everyone should put in the back of their mind. Then, when the context of the question is somewhat forgotten, the question should be pulled out and applied to the self. Are you (that's YOU) a mouth breather? Because you shouldn't be...unless you're doing one of the following:
1. walking super fast
3. yelling a lot
4. having sex (perhaps this could be rolled into #3)
Please shut your damn mouth. No one wants to smell the odor of your breath. Everyone hates your breath. Whether it smells good OR bad, it is a private thing - similar to the smell of one's genitalia; only to be shared in the most intimate of situations. Breathe through your nose...and quietly. I work with a man who I can continuously hear breathing. Granted, he's not breathing through his mouth (thank God) but the sound of air whistling through his nose is so prominent I often think there is a draft.
If you find yourself needing to breathe through your mouth when you are not doing one of the approved activities, please get yourself to a gym so you can improve your lung capacity. Now.