The most effective way to improve your indoor air quality is a combination of three things: reducing pollution sources inside your home, increasing ventilation, and filtering the air that remains. Most people focus on just one of these, but they work best together. Indoor air can be two to five times more polluted than outdoor air, largely because homes trap emissions from cooking, cleaning products, furniture, and other everyday sources in a relatively small space.
Control Pollution at the Source
Removing or reducing the things that pollute your air in the first place is more effective than trying to clean the air after it’s already contaminated. The EPA identifies a long list of common household sources of volatile organic compounds (VOCs): paints and paint strippers, aerosol sprays, cleansers and disinfectants, air fresheners, moth repellents, hobby supplies like glues and permanent markers, pesticides, and even dry-cleaned clothing. New furniture and building materials also release VOCs, particularly formaldehyde, for weeks or months after installation.
A few chemicals deserve special attention. Benzene is a known human carcinogen, and the main indoor sources are tobacco smoke, stored fuels, paint supplies, and automobile emissions that drift in from attached garages. Methylene chloride, found in paint strippers and aerosol spray paints, causes cancer in animals. Perchloroethylene, the chemical used in most dry cleaning, has the same concern. When you bring home dry-cleaned clothes, let them air out in a well-ventilated space before hanging them in a closet.
Switching to low-VOC or fragrance-free cleaning products, avoiding aerosol sprays when liquid alternatives exist, and storing fuels and solvents in a detached garage or shed can meaningfully cut the chemical load in your home without spending money on equipment.
Deal With Your Gas Stove
Gas stoves are one of the largest sources of indoor air pollution in homes that have them. Research has shown that just a few minutes of gas stove use can push nitrogen dioxide levels past outdoor air quality limits set by the EPA and the California Air Resources Board, sometimes exceeding the World Health Organization’s 24-hour guideline by an order of magnitude. A Stanford study also found that gas stoves generate benzene at levels that can exceed both EPA and WHO benchmarks.
If you cook with gas, the single most important thing you can do is use a range hood that vents to the outside. “If you’re going to have a gas or LPG stove, you need a vented hood to be able to reduce pollutants inside the home. That is for certain,” says William Checkley, a professor of medicine at Johns Hopkins University who has studied cooking pollutants extensively. Many range hoods simply recirculate air through a charcoal filter without venting outdoors. These are far less effective. If your hood doesn’t vent outside, opening a nearby window while cooking provides a meaningful alternative.
Increase Ventilation
Fresh air dilutes indoor pollutants faster than almost anything else. A Lancet Commission report proposes that four air changes per hour (ACH) qualifies as “good” indoor air quality, six ACH is “better,” and above six is “best.” The CDC recommends aiming for at least five ACH in workplaces to reduce airborne viral particles, and the same principle applies at home.
In practical terms, an air change means replacing the full volume of air in a room. You don’t need special equipment to improve this. Opening windows on opposite sides of your home creates cross-ventilation that moves air through quickly. Running bathroom and kitchen exhaust fans pulls stale air out. Even cracking a window in a room where you spend a lot of time makes a difference, especially if you’re doing anything that generates pollutants like cooking, cleaning, or working with adhesives.
The obvious exception is when outdoor air quality is poor. During wildfire smoke events, high-pollen days, or if you live near a busy highway, keeping windows closed and relying on filtration is the better strategy.
Use Air Filtration Effectively
If you have central heating and cooling, upgrading your filter is one of the easiest improvements you can make. The EPA recommends MERV 13 or higher rated filters for better particle removal, though you may need an HVAC technician to confirm your system can handle the increased airflow resistance. Most disposable filters last three to twelve months depending on thickness, but check yours monthly. If it looks visibly dirty, replace it regardless of how long it’s been.
For rooms where you spend the most time, a portable air cleaner with a HEPA filter adds another layer of protection. When shopping, look at the Clean Air Delivery Rate (CADR) listed on the unit, specifically the number for “dust.” Harvard’s Healthy Buildings program suggests sizing your air cleaner so the room gets the equivalent of at least four to six effective air changes per hour. A unit with a CADR that’s too low for your room size will run constantly without making much difference. Manufacturers typically list the maximum room size on the box, but sizing down (using the cleaner in a smaller room than rated) gives you better results.
If you can’t afford a commercial air purifier, a surprisingly effective alternative is a DIY air cleaner: a box fan with one or more furnace filters attached using tape or bungee cords. The EPA acknowledges this as a reasonable temporary option, particularly during wildfire events.
Keep Humidity in the Sweet Spot
The EPA recommends keeping indoor relative humidity between 30 and 50 percent. Above 60 percent, condensation forms on surfaces and creates conditions for mold growth. High humidity also encourages dust mite populations to thrive, which is a major trigger for allergies and asthma. Below 30 percent, you get dry airways, cracked skin, and increased susceptibility to respiratory infections.
A simple hygrometer (available for under $15) tells you where you stand. In humid climates or seasons, a dehumidifier or air conditioner keeps levels in range. In dry winter months, a humidifier helps, but set it below 60 percent and clean it regularly to avoid growing mold in the unit itself. Fixing leaks promptly, using exhaust fans while showering, and not drying laundry indoors all help keep moisture under control.
Skip the Houseplants (for Air Quality)
The idea that houseplants clean indoor air traces back to a NASA study conducted in sealed laboratory chambers. A comprehensive review by researchers at Drexel University found that the results don’t translate to real homes. The natural air exchange in a building, even with windows closed, dilutes VOCs orders of magnitude faster than plants can absorb them. By their calculations, you would need between 100 and 1,000 plants per square meter of floor space to match the cleaning capacity of a couple of open windows. Plants are great for other reasons, but air purification isn’t realistically one of them.
Monitor Your Air to Know What’s Working
An indoor air quality monitor that tracks particulate matter (PM2.5) and carbon dioxide (CO2) gives you real feedback on whether your efforts are working. CO2 levels rise when a room is poorly ventilated with people in it, so a climbing CO2 reading is a straightforward signal to open a window or turn on ventilation. A spike in particulate matter while cooking tells you your range hood isn’t doing enough or that you need to open a window.
There are currently no widely accepted indoor thresholds for most pollutants, and the alert levels on consumer monitors are set by each manufacturer rather than standardized. But the World Health Organization’s 2021 guidelines recommend annual average PM2.5 exposure below 5 micrograms per cubic meter, down from 10 in the previous guidelines. Most populated areas worldwide don’t meet even the older standard. Using a monitor to keep your indoor PM2.5 consistently below outdoor levels is a practical, achievable goal.
During Wildfire Smoke or High Pollution Events
When outdoor air quality is hazardous, the strategy flips: instead of ventilating, you want to seal your home and filter aggressively. The EPA recommends creating at least one “clean room” in your home. Close all windows and doors, run a portable air cleaner or DIY box fan filter, and avoid activities that add particles indoors like frying food, burning candles, or vacuuming without a HEPA-equipped vacuum. If you have central HVAC, set the fan to run continuously with a MERV 13 or higher filter to keep circulating and cleaning indoor air even when the system isn’t actively heating or cooling.