There are a a couple signs you need house ventilation, starting with:
1. Enduring odors
If you have issues getting potent odors out of your space, you could have a ventilation problem.
2. Stuffy air
The air in your house should be fresh, but musty zones mean you likely have insufficient ventilation.
3. Disproportionate dust
Dust can build up more frequently in areas with inadequate ventilation.