Can Dry Indoor Air Cause Respiratory Symptoms?
Can dry indoor air cause respiratory symptoms?
Yes, in two ways. Below about 30 percent relative humidity, the mucous membranes in your nose and throat dry out, which weakens their first-line defense against particles and viruses. Dry air also lets respiratory viruses stay infectious longer in the air. In heating season, indoor humidity routinely drops into the teens in many U.S. homes.
Why this matters: a review of indoor air humidity and health in the International Journal of Hygiene and Environmental Health summarized evidence that low indoor humidity contributes to eye irritation, dry skin, and upper airway symptoms, and that very dry air affects how respiratory viruses transmit (Wolkoff, 2018). ASHRAE's comfort standard 55 recommends a humidity range that overlaps with the 30 to 50 percent IAQ window.
How to investigate:
Use a hygrometer for one heating-season week. If your living and bedroom spaces stay below 30 percent for hours at a time, that's the issue. Before you buy a humidifier, look at envelope air leakage. Excess outdoor air infiltration in winter drops indoor humidity even when you're producing moisture inside. Sealing the right gaps is often cheaper than a humidifier and prevents downstream maintenance.
Watch the 60-second breakdown:
The free 8-minute assessment will help you decide whether dry air is the right thing to spend on, or whether something else is upstream of it:
