There are a a variety of indications you might require house ventilation, including:
1. Lingering odors
If you have problems getting strong aromas out of your space, you might have a ventilation issue.
2. Stale air
The air in your rooms should feel fresh, but stale spots mean you could have issues with ventilation.
3. Disproportionate dust
Dust can get stuck more often in rooms with stifled airflow.