What can I do to remove the old house smell from my 100 year old house

It might be coming from the floors. If they are wood, you may need to reseal them. Put boxes of baking soda near the really smelly areas, and go to the dollar store and get some of those things that absorb water. They are sort of a triangle shape and look empty. Once you take the foil off of the top, put them in several areas and, over time, they will fill up with the excess moisture that's around.

Here's some advice from another owner of an old house. Hope it might help you? https://ahairinmybiscuit.com/how-i-rid-my-old-house-of-musty-odors/

Most smells are absorbed into soft materials like fabric, curtains, carpet. Are you sure it isn't an odor from a damp basement? My house has only a partial concrete floor (it's an old house) and the dirt parts make it musty at times. A dehumidifier helps. Were the previous owners smokers? I am amazed how the tar and nicotine clings to things. We used to own a rental, and for six months, there were heavy smokers living there. After cleaning, I had to repaint with sealer first, steam clean the carpet twice, air the place out for days. I think the ceilings were the worst, since the sticky stuff of heaviest there. I've also used an air cleaner with good results.

I learned about these only this week. I have not tried them, but have read many positive things about them. You might need one in every room and closet. Hope this helps.

sorry , forgot the info (duh me!) here it is: NatureFresh Air freshner good for mold, mildew, bacteria and other foul odors and causes. Hope this helps

Get a whole bunch of damp rid, comes in hanging pouches tubs n keep replacing till smell goes away, bout month or 2..

Clean as much as you can with vinegar! Dehumidifiers do work to reduce the musty smell. Nicotine stained walls should be cleaned with vinegar, painted with sealer then painted with color. Fabrics should be steamed cleaned.