There are a a variety of signs you might require house ventilation, including:
1. Ever-present odors
If you have trouble getting powerful aromas out of your space, you likely have a ventilation problem.
2. Stuffy air
The air in your space should be fresh, but stuffy zones mean you could have inferior ventilation.
3. Disproportionate dust
Dust can build up more quickly in rooms with insufficient airflow.