There are several low-to-no-cost steps you can take now to improve the indoor air quality in your home and reduce your exposure to asthma triggers, radon, mold, carbon monoxide, and other indoor pollutants. These actions include controlling the sources of pollution, changing filters, and keeping humidity below 60% (ideally, 30-50%). Learn more about the specific steps you can take at: https://www.epa.gov/indoor-air-quality-iaq/improving-indoor-air-quality.
If you are remodeling or improving the energy efficiency of your home, steps should be taken to minimize contaminants from sources inside the home. These sources may include off-gassing from paints, cabinetry, carpets, and other new materials, or from disturbing materials already in the home, such as lead-based paint and asbestos insulation. In addition, remodeling efforts should pay particular attention to preventing moisture from entering the home and in ensuring proper ventilation to remove moisture, combustion gases, and other contaminants from the home. More remodeling tips can be found here.
If you are in the market for a new home, look for the Indoor airPLUS label. Homes built with the Indoor airPLUS label are designed for improved indoor air quality compared to homes built to minimum code. For more information, see: https://www.epa.gov/indoorairplus/basic-information-about-indoor-airplus.