There are a a couple warning signs you should consider house ventilation, starting with:
1. Persistent odors
If you have problems getting intense smells out of your home, you likely have a ventilation problem.
2. Stale air
The air in your rooms should feel fresh, but stale zones mean you might have issues with ventilation.
3. Lots of dust
Dust can get stuck more often in homes with inadequate airflow.