We also don’t have any trouble inhaling other people’s stale carbon dioxide, even with a solid few feet between us. Though we don’t yet have a decisive scientific explanation for this olfactory phenomenon, there’s no shortage of promising theories. As HowStuffWorks reports, another hypothesis suggests that we’re more conscious of other people’s halitosis because breath released when speaking is different than breath released when exhaling regularly. But if that’s true, it seems like you’d be able to smell your own breath—at least when you’re the one doing the talking. When someone else exhales, you’re inhaling their air almost simultaneously.