A friend had an electrical fire in a gazelle. I was occupying the left hand seat in a warm friendly daze when I sniffed the air and indicated we may have to land. He was slightly non-plussed as he could not smell anything.
Later I asked why he hadn't noticed the all pervasive scent of burning wires.
"I don't have any sense of smell."
"Didn't they pick that up at your medical?"
"They never asked."

