Home Air Quality Risk Estimator
Our ai enhanced tool computes home air quality risk accurately. Enter your inputs for detailed analysis and optimization tips.
Formula
Indoor AQI = Outdoor AQI x Infiltration x Ventilation x Purifier + Indoor Sources
Indoor AQI is calculated by combining outdoor pollutant infiltration (based on building envelope tightness, ventilation type, and purifier effectiveness) with indoor-generated pollutants (from occupants, cooking, and household sources). Each factor reduces or contributes to the total indoor air quality index.
Frequently Asked Questions
Is indoor air quality really worse than outdoor?
The EPA estimates that indoor air can be 2-5 times more polluted than outdoor air, and in some cases up to 100 times worse. This is because indoor environments concentrate pollutants from multiple sources: cooking (PM2.5, NO2), furniture off-gassing (VOCs, formaldehyde), cleaning products, mold, pet dander, and human bioeffluents. Unlike outdoor air which disperses pollutants over large volumes, indoor air recirculates in enclosed spaces. Americans spend approximately 90% of their time indoors, making indoor air quality arguably more important than outdoor AQI for overall health. Proper ventilation and filtration are essential for maintaining healthy indoor environments.
How does home age affect indoor air quality?
Home age affects air quality in two competing ways. Older homes (pre-1990) tend to have leakier building envelopes with higher natural infiltration rates, meaning outdoor pollutants enter more freely but indoor-generated pollutants are also diluted faster. Newer homes (post-2000) are built much tighter for energy efficiency, which reduces outdoor infiltration but can trap indoor pollutants if not properly ventilated. Very new homes also have higher VOC levels from new construction materials, paint, and furniture. The sweet spot is a well-sealed home with mechanical ventilation and filtration, which controls both outdoor infiltration and indoor buildup.
How effective are HEPA air purifiers for indoor air quality?
HEPA air purifiers are highly effective for particulate matter, capturing 99.97% of particles 0.3 microns and larger. In real-world home use, a properly sized HEPA purifier can reduce PM2.5 levels by 40-60% in the room where it operates. However, effectiveness depends on several factors: the unit must be sized for the room (look for CADR rating matching room size), filters must be replaced regularly (typically every 6-12 months), and doors/windows should remain closed. HEPA purifiers do not remove gases like CO2, VOCs, or radon. For comprehensive air quality improvement, combine HEPA filtration with adequate ventilation and source control (reducing pollutant generation).
Should I keep windows open or closed for better air quality?
The answer depends on your outdoor AQI. When outdoor AQI is below 50 (Good), opening windows provides beneficial ventilation that dilutes indoor pollutants and replenishes oxygen. When outdoor AQI is 50-100, balance is needed — brief airing during low-traffic hours (early morning) is acceptable. When AQI exceeds 100, keep windows closed and rely on mechanical filtration. During wildfire smoke events (AQI 150+), sealing the home and running HEPA purifiers is essential. A compromise solution is a heat recovery ventilator (HRV) with MERV-13+ filters, which provides continuous fresh air while filtering outdoor pollutants. Season also matters — pollen counts affect the optimal window strategy for allergy sufferers.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.
What formula does Home Air Quality Risk Estimator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.