Poor ventilation is a bigger problem than most people realize. It's also an issue that follows us to work as many workplaces have poor ventilation too.
While humidity is definitely something to consider, VOCs and Carbon Dioxide levels are also important.
Two other suggestions that can help:
1. Passive vents
2. Door undercuts or gaps that leave a space at the bottom of the door
It's a tricky balance in winter time since most people want to reduce drafts, but doing that can often make the air quality worse.