Current Air Quality – Spokane Regional Clean Air Agency

What does Current Air Quality represent?

Pollutant concentrations are converted to the Air Quality Index (AQI). The pollutant with the highest value (the predominant pollutant) is reported for the “Current Air Quality.” The AQI is updated each hour.

The air quality monitoring network measures concentrations of three air pollutants: PM10 (coarse + fine particles), PM2.5 (fine particles) and Ozone (measured May-Oct during ozone season.) The monitoring map (above) provides data for each monitoring site in Spokane County. You can view the current day trend, or you can view a 5-day trend for each site. Some sites measure multiple pollutants.

How is the AQI calculated for the Current Air Quality?

Each pollutant has its own health-based standard. For particulate matter, it is a 24-hour average, midnight-to-midnight. This means the official daily AQI is not known until the following day. A rolling 24-hour average report also isn’t very useful when conditions rapidly change, such as during a dust storm or wildfire. To address this, EPA developed the NowCast to report air quality that is near real-time (referred to as “Current Air Quality” reported at the top of this webpage.)

The NowCast calculation is designed to be responsive to rapidly changing air quality conditions.  More recent hourly air pollution readings (e.g., last three hours) are given greater weight in determining the NowCast index value when air quality is changing more rapidly, as may be the case when wildfire smoke affects air quality. 

Why don’t we provide a one-hour, stand-alone value? Because there is not a one hour health-based standard. For ozone, the standard is an eight-hour average, and for particle pollution it is a 24-hour standard. The NowCast is a very effective tool to report near real-time air quality that correlates to the health-based standards. Learn more about the AQI and NowCast calculations.

Why is the AQI updated only once an hour?

Each hour, readings from our air quality monitors are automatically uploaded to the statewide air quality monitoring telemetry system and then to EPA’s AirNow.gov.  Data goes through a quality check, and then at :35 past each hour, our website is updated with the most recent hour of data. So, the Current AQI updated at 1:35 pm is monitored data from Noon-1pm.  At 2:35 pm, the 1-2 pm data is reported.  The delay enables our system to ensure we are providing the best quality data. If a monitoring site has a malfunction, this potentially “bad data” can be removed from the reporting so that the AQI isn’t erroneously reported.

What does “Unhealthy for Sensitive Groups” mean?

If the AQI is over 100 then it is in the Unhealthy for Sensitive Groups/Orange range. This means the air quality is not meeting the federal, health-based air quality standard.

Inhaling smoke is not good for anyone, even healthy people. Most people are likely to have minor symptoms. Several groups of people, especially those with pre-existing heart and lung conditions, are more at-risk for severe health impacts. People most likely to have health problems from breathing smoke include:

• Lung diseases such as asthma or chronic obstructive pulmonary disease (COPD), including bronchitis and emphysema.
• Respiratory infections, such as pneumonia, acute bronchitis, bronchiolitis, colds, or flu.
• Existing heart or circulatory problems, such as dysrhythmias, congestive heart failure, coronary artery disease, and angina.
• Prior history of heart attack or stroke.
• Infants and children under 18 because their lungs and airways are still developing and they breathe more air per pound of body weight than adults.
• Adults over age 65 because they are more likely to have unrecognized heart or lung diseases.
• Pregnant women because both the mother and fetus are at increased risk of health effects.
• Smokers because they are more likely to already have lower lung function and lung diseases.
• People with low socioeconomic status because they are more likely to have higher exposures and less likely to have access to healthcare.

How does Spokane Clean Air measure air pollution?

We operate a network of monitoring sites in Spokane County, each with sophisticated instrumentation that collects concentrations of air pollutants every hour, around the clock.  The pollution concentrations are submitted to the state department of Ecology and the US Environmental Protection Agency (EPA).  Cities across our country are required to monitor compliance with health-based air quality standards for specific pollutants commonly found in ambient air and that pose a risk to human health and the environment.

How is the 2-day Air Quality Forecast developed?

A member from our experienced air quality monitoring section develops a two-day air quality forecast each morning. Air quality forecasting is challenging, especially for wildfire smoke because conditions can change so rapidly. Several sources of data and information are reviewed and considered when developing the daily forecast, including:

• The current air quality trends
• Weather reports, trends and forecasts
• Smoke and active fire maps and models (during wildfire season)
• Satellite images
• Conference calls with other air quality and weather agencies during widespread events such as wildfires and dust storms.

Why isn’t there an air monitoring station closer to my home?

There are specific ambient air quality monitoring protocols outlined by the EPA that air quality agencies must follow. These requirements ensure that a community’s ambient air quality is measured effectively to determine if air quality standards are being met.  Ambient air quality monitoring is done at the neighborhood scale (representative of neighbor air quality) and at the community scale. While air quality can vary somewhat neighborhood to neighborhood, locations are selected to represent air quality over broad areas. For example, there are two monitoring sites that represent neighborhood air quality and others that represent community air quality. The emphasis is on areas expected to have the worst pollution as well as to avoid redundancies among locations.

Why is the air quality reported at AirNow.gov sometimes different than what is reported at SpokaneCleanAir.org?

AirNow.gov and Spokane Clean Air report the same air quality data which come from the regulatory monitors in Spokane County. For short periods of time, the websites report different values only because the two websites update at slightly different times.

Why do the monthly air quality reports list AQI values lower than I recall seeing on the current Air Quality webpage?

The monthly air quality reports provide the maximum AQI for each day of the month. On our website, we provide near real-time air quality. The national, health-based standards are not hourly or realtime. Particulate matter (PM) is a 24-hour average, midnight to midnight. Ozone, it is the max 8-hour running average for the day. While you may see slightly higher hourly AQI values, until the day is over, the official 24 -hour average (PM) and max 8-hour average (Ozone) cannot be calculated until the day is over. To read more information related to this topic, review the questions/answers provided above.

What are personal air sensors?

Why doesn’t data from my PurpleAir sensor align with what Spokane Clean Air is reporting?

PurpleAir data can report in different time increments, whereas regulatory monitors capture hourly data. This is why it is important to look at the data details. Here are some tips:

If you are looking at the Purpleair.com/map and want to compare Purple Air sensor data with regulatory, stationary monitoring site data, an equation has been developed by agencies, including EPA, that helps corrects the PurpleAir data. When looking at the PurpleAir map, in the lower left corner there is a box where you can select “Conversion” then select “US EPA” and then “one hour average graphs” to see the most comparable data to what is reported at SpokaneCleanAir.org and AirNow.gov and which corresponds to health-based air quality standards.