There are a a couple indications you should have house ventilation, including:
1. Ever-present odors
If you have problems getting intense odors out of your house, you may have a ventilation issue.
2. Stuffy air
The air in your space should feel fresh, but stale zones mean you could have insufficient ventilation.
3. Disproportionate dust
Dust can get stuck more quickly in areas with inadequate airflow.