Strange smell

This question pertains to my father who rarely visits the Dr.
He is 82 yrs old and he has congestive heart failure.
As of late, he says he experience a strange smell in the middle of the night, actually from 11pm to 400am. He says it smells like a "deadly gas smell" (for lack of a better description).
There are no strange smells in the house or the immediate area outside. Nor can anyone else smell this odor.
Could this be a medical condition ?

[cybermyra]

Does your Dad have any mental problems? These smells might be delutional , smells that aren,t there are like voices that aren,t there, and sence they are at night, when the elderly tend to be more cofused. I would take him to see a neurolgist, smells could also mean something in the brain. any way he could be evaluated.

[amosbo2003]

I have heard people smell burning hair smell when a stroke is coming on.  

[pepe_le_pew_lover]

I also think the problem might be neurological... I don't know if it's a stroke or anything else, but a few neurodegenerative diseases, like Alzheimer's, start by probs concerning the smelling sense. Considering his age, I would say it might be helpful to take him to a neurologist... if he refuses, just have one stop by the house... I think docs can do that for someone his age... no point in tiring him.

Good luck! :)

[sonnilbee]

I have been experiencing an unpleasant odor and it only happens when i am on the subway or in the bus. I do not get it anywhere else. I have been to a doctor and she is out of ideas. I have tried every known home remedy and nothing. It is strange since I only get it on public transportation. It is really stressing me out.

Can anyone please help me?