bad smell

Why do I smell something bad when something bad is happening to me?  When I burn myself I smell something bad really fast and then it's gone.  The same thing happens when I trip and I'm scared about falling.  My heart rate goes up and I smell something bad, but I calm down rather quickly and the smell goes away.  Most concerning I started smelling this smell again for no clear reason but it continuted longer than usual and then I felt as though I was about to pass out.  Why am I smelling this same indescribable smell everytime something seems out of sorts with my body?