A dry, well ventilated home is a healthy home.  You can survive 3 weeks without food, 3 days without water and about 3 minutes without air. If you have a well sealed home then you are likely not getting enough fresh air.  If you live in a busy urban environment where you close windows and doors for security or noise reasons then you are likely to not having enough fresh air.  Your home is your castle – make it a healthy one.  See HRV