Have a wood burning fireplace in family room of a house recently purchased.
After burning Duraflame or Northland logs the next morning the house smells
like a campfire doused with water. THe odor last 2-3 days. I have tried
leaving
the flue open till the next morning and closing it an hour or so after logs
are
burned up. Any ideas what could be causing this?

Sounds like inadequate draft.
If you have been closing the damper, try leaving it open.
Alternatively, the chimney height or placement may promote downdraft.

My brother has the same problem. They've had the chimney cleaned several times
with no luck. The last one told them that he thought the chimney height and
proximity to the roof might be causing a down draft in the flue.

Is there a fan or something that can be added to the chimney?? Or are they
just stuck to not being able to use the fireplace?