As temperatures climb and heatwaves intensify, Americans are once again retreating indoors to escape the sweltering sun. But while air conditioning (AC) offers critical protection from extreme heat, experts warn that excessive use of climate control can carry its own health risks if not carefully managed.
Air conditioning has become a staple of modern summer living, especially in the U.S., where its widespread adoption since the 1960s has encouraged people to spend more time inside. And with good reason: AC can be life-saving. According to the CDC, heat-related deaths in the U.S. have doubled from 1999 to 2023, particularly affecting vulnerable groups such as the elderly and immunocompromised.
Beyond cooling, AC units also help filter air, reducing indoor exposure to pollutants like dust, pollen, and PM2.5—dangerous particles linked to heart and lung disease. “Every time the AC system operates, it’s pulling some particles out of the air,” says Brent Stephens, professor of environmental engineering at Illinois Institute of Technology. This makes AC especially valuable in areas affected by wildfire smoke, traffic emissions, or industrial pollution.
However, doctors and engineers caution that poorly maintained or overly dry AC environments can cause respiratory issues. “Spending too much time in air-conditioned rooms can lead to more respiratory symptoms,” says Dr. William Checkley, a pulmonary specialist at Johns Hopkins. The dry air created by overuse of AC can irritate airways, causing sore throats, congestion, and inflammation—a condition known as “sick building syndrome.”
Children and those with weakened immune systems may be particularly susceptible, as dry indoor air can weaken the lungs’ defenses against infections. Viruses also spread more easily in dry environments, similar to the effect seen during long airplane flights.
Experts recommend maintaining indoor humidity levels between 40% and 60% to avoid the twin dangers of mold (in overly damp air) and respiratory issues (in dry air). A simple tool called a hygrometer can help track humidity levels.
Regular AC maintenance is also essential. Dirty filters can circulate mold, bacteria, and allergens throughout a home. Experts advise replacing filters every one to two months during peak use and investing in filters with MERV ratings of 11 or 13 for optimal air quality.
Additionally, while AC filters trap particles, they do not eliminate volatile organic compounds (VOCs)—gases released by household products like furniture, cleaners, and air fresheners. These chemicals can irritate the respiratory system and disrupt indoor microbial balance. For this reason, experts suggest using air purifiers to complement AC systems and improve indoor air quality.
As summer heat becomes more extreme, AC remains a critical tool. But with proper maintenance and balanced use, it can protect both comfort and health.
