Does anyone diagnosed with dementia experience smells that aren't there?

The answer is yes, of course. Anyone whose brain is malfunctioning has manifestations of hallucinagenic items they deem are real. They are not. A person may have their own voice and the voice of someone they think is talking to them. They may hear voices, see things that aren't there, etc.

Has anyone else in your household noticed a recurring odor? Does the smell occur wherever you go? I would definitely get this checked out, especially if you answered no to the first question and yes to the second one. (Responding to your Q about the possibility of dementia, my mother with advanced condition has never reported smelling anything unusual even in the beginning stages when she could still distinguish reality from fantasy.)

If it's a day to day thing, please consider the advice given here. (If it's sudden, it could indicate a stroke is imminent. I saw that on the tv show 'Mad Men', Betty's dad had dementia and smelled oranges.)

It is interesting that it is the same smell every time and for about the same duration. Its not just increased smell 'sensitivity' or awareness of different smells. So it really is a neurologic phenomenon.

While most people associate the word "hallucinations" with seeing things that aren't there they can include hearing, smelling, tasting or feeling things that are not real. PD and ALZ are both known to cause hallucinations... I hope the "smell" isn't too unpleasant?

I've also heard smells can occur with brain tumors so definitely get it checked out.

What you're describing sounds to me like a seizure aura, which is really a warning sought before a seizure. I've never heard of anything like you're describing except for a seizure, anything else would seem to me like it's way out there. I dealt with two people who at some point or another develop some form of dementia, and neither one of them experienced anything like you're describing

Phantom smells are also associated with stress. I'd discuss it with your doctor. I've read about them online quite a bit, since it runs in my family. I know. Odd.

They can occur in one or both nostrils. The phantom smell may seem to always be present or it may come and go. Phantosmia may occur after a head injury or upper respiratory infection. It can also be caused by temporal lobe seizures, inflamed sinuses, brain tumors and Parkinson's disease. Please see a good Neurologist for some testing.