The Data Behind Air Factor™

Air Factor™ uses the First Street Air Quality Model to find air quality risks across the United States

The First Street Air Quality Model is focused on how climate change is impacting air quality conditions within the US. Increases in wildfire occurrence and climatic conditions favorable for ozone formation are forecast to be the largest impacts of climate change on air quality. The model builds off of decades of scientific peer-reviewed research and forecasts how outdoor air quality and resulting indoor air quality within structures will change over time due to changes in the environment.

Analyzing major pollutants

The First Street Air Quality Model considers a location’s current and future risk from the two most common harmful air pollutants: fine particulate matter (<2.5 ug) and ground-level ozone. Fine particulate matter, or PM2.5, is emitted by wildfires and man-made sources including vehicles, fuel combustion, or power plants. Ozone forms when pollutants emitted by sources including cars, power and chemical plants, refineries, chemically react in the presence of sunlight. To build an understanding of air quality risks, Air Factor combines simulations of wildfire smoke from fires in the the First Street Wildfire Model and state-of-the-art chemical transport models from the EPA. For every location, likely exposure to air pollution is calculated today and 30 years into the future, taking into account environmental changes that affect PM2.5 and ozone formation. 

Note that while PM2.5 and ozone are the primary sources of climate-related poor air quality days in the US, other air pollutants may also contribute to broader air quality concerns and have adverse health effects. At this time, we do not include other pollutants in the model, but do flag the top 25% of industrial facilities’ hazard levels in the EPA’s Toxic Release Inventory database for consumer awareness.


Calculating and mapping air quality risks

The First Street Air Quality Model is a climate-adjusted model, which means it considers how a location’s likely exposure to ozone and particulate matter is affected by rising temperatures and changing humidity levels. Outdoor air quality levels are combined with property characteristics like insulation and air filter ratings to provide an understanding of indoor air quality during poor outdoor air quality days. 

The model builds a forecast of the expected annual number of poor Air Quality Days as defined by the EPA Air Quality Index (AQI 100+) for each location in the US by using chemical and particle transport models from the National Oceanic and Atmospheric Association (NOAA), Environmental Protection Agency (EPA), climate models from the WCRP CMIP6, and wildfires from the First Street Wildfire model. Local variation in air quality is driven by high resolution climate variation, proximity to wildfire activity, and other emission sources. 

Note that other related climate risks from wildfires, including burn probabilities and ember risk, are considered in the Fire FactorTM model, also available from First Street .

Determining future air quality levels

The inclusion of environmental changes that impact future air quality risk are an essential part of the First Street Air Quality Model. The model uses the WCRP CMIP6 SSP245 scenarios to forecast how environmental conditions will change 30 years into the future and how those conditions will influence ozone formation and PM2.5 levels from increased wildfire activity. This allows the First Street Air Quality Model to predict outdoor and indoor poor air quality days today and 30 years from now in a way that meets the standard of scientific peer review.

Simplifying air quality risks

Air Quality strongly impacts the liveability of a property or community, yet most air quality forecasts only provide near real-time information on air quality conditions. For an analysis of air quality to be useful to a property owner, it has to provide specific information about air quality conditions throughout the year. This includes both day to day air quality levels from human  sources and extreme conditions from events like wildfires. The First Street Air Quality Model combines all these sources into a straightforward representation of “poor air quality days”, alongside actionable recommendations for different levels of severity.

Scoring system for properties

Once the number of days at varying air quality severity levels (AQI categories) have been calculated at a property-level for both this year and 30 years into the future, the aggregate number of poor air quality days over that time period is taken in order to arrive at a single score that represents how likely a specific location is to experience poor air quality. A property’s Air Factor™ is based on that 30 year estimate, which means that a property with a higher Air Factor™ has a higher likelihood to experience poor air quality days today and in the future than a property with a lower Air Factor score.

Measuring indoor air quality

Given outdoor air quality concentrations and information about a building, it is possible to estimate the indoor air quality. In conjunction with Arup, a global engineering firm that specializes in structural engineering and damage estimates, First Street has developed an estimate of indoor air quality levels for every building affected by poor air quality days. Indoor air quality days are categorized on the same Air Quality Index categories that are used for outdoor air quality. A building’s filtration system, insulation, and presence of air purifiers all impact indoor air quality levels. The First Street Air Quality Model combines industry standards and user inputted data on building characteristics to estimate indoor air quality levels from outdoor air quality levels.

Ensuring scientific accuracy

The First Street Air Quality Model brought together top climate scientists, modelers, engineers, technologists, and analysts. Results of the model have been compared against historical air quality observations at regulatory grade EPA measurement stations to ensure scientific accuracy wherever possible. Using Open Science protocols, all methods used by the First Street Air Quality Model have been published or submitted to scientific journals and are open to review on the Risk Factor website.

Continuously improving over time

First Street has made its air quality model’s full technical methodology available to the public because it supports scientific collaboration and data transparency. The First Street Air Quality Model will continue to incorporate feedback and improve its model over time, including annual data updates as new data become available.

Why are air quality risks increasing?

A changing environment means higher temperatures and changing humidity, creating conditions which facilitate ozone formation and more wildfire activity.

What can be done to address air quality risks?

Although air quality risk can never be completely eliminated, there are a number of steps homeowners can take to understand and reduce that risk.

Share This Page

Share Facebook
Share Twitter
Share LinkedIn
Share Email

Page URL