How to get rid of old house smell?
Years ago, my wife and I moved into a condo that had a faint weird smell. I put charcoal into a net  bag like the ones potatoes come in, and set it into the cold air return ducting at the furnace. I then set the fan to run continuously. We also put the same netted bags in some of the other rooms. After a few weeks the smells were gone. The charcoal absorbed the odors. We built our present house 20 years ago. My wife has a very sensitive nose and detects every odor. I had the furnace guy install a special filter rack where I insert a charcoal filter into this rack ahead of the normal air filter. This charcoal filter takes out almost every conceivable odor that is in the air. Of course, I have run my furnace fan 24/7 for 20 years and counting.  I buy mine at Home Depot or Lowes. They have a plastic frame that can be cut to size to fit the filter rack. No odors in my house (happy wife- happy life). This worked for me.