Relative Humidity inside a House

I recommend a range of 30% to 50% of relative humidity for comfort and health. Below 30% relative humidity begins to dry out the nasal passages and our sinuses which can lead to more colds and flu susceptibility. If you are COPD, have allergies or have respiratory problems your physician may have a more appropriate range for unique health and comfort. Above 55% dust mites begin to thrive and other insects and unhealthy things. I therefore recommend a range of 30-50% for best results. Too dry causes house problems of cracking drywall & plaster, shrinking hardwood floors, furniture cracking, trims separating, and cabinetry joints showing cracks. Like our bodies, a house has a range for comfort and optimal performance.