What Causes Bad Odor From Nose Along With Thick Mucus Drainage?

For the last several months, I have periodically smelled a dirty ashtray type smell that doesn t exist. It started after we had a fire in our fireplace and the smoke backed up in our house. I don t even know if the two situations are related, but that is the only marker I have for when this started. There is no rhyme or reason to the smell, although it does appear to be worse in the later part of the day. Some days I have it frequently, other days only a few times, and sometimes not at all. I do have some very thick clear mucous that I occasionally blow out of my left nostril, but that has been an issue for a few years, the smell started around January.