Air Quality Index – how is the value determined?

Let’s take a moment to get acquainted with how air quality is measured and what that means for you specifically. On the main page of this blog you’ll find a map of air quality monitors around the region. What exactly do those colors mean and how is the Air Quality Index (AQI) value determined?

The AQI is a nationally uniform color-coded index for reporting and forecasting daily air quality. In this case, the AQI is being used to communicate the level of PM 2.5 present. We reviewed what PM 2.5 is and its effects last fall. There is a national air quality standard for PM 2.5 and the 24 hour average standard is set at 35 ug/m³. The pollutant is measured hourly and those values are averaged to get the PM 2.5 value.

When related to the AQI, the 35 ug/m³ value standard is the threshold where air quality crosses over from “moderate” to “unhealthy for sensitive groups.” Rather than give you measurements of PM 2.5 which can be confusing, the EPA translates that to the AQI values to communicate risk to you. Check out the image below to see what the values are, who needs to be concerned at each level, and what they should do.

EPA Air Quality Index

What’s an Air Resource Advisor ?

A lot of people wouldn’t know this but an “air resource advisor” is often deployed to large, catastrophic wildfires. Air resource advisors (ARAs) are technical specialists with expertise in air quality science. The position came about from the partnering of multiple state, federal, and tribal agencies that recognized the need to be proactive about smoke impacts on communities.

ARAs are trained in smoke modeling, air quality monitoring, health risks from smoke, and impact mitigation. During a wildfire incident, they set up shop at the fire camp and communicate in-depth smoke impact information and forecasts to fire incident teams, air quality regulators (us here at DEQ), and the public. When fire season gets in full swing, you may see some ARA publications put on this site. It usually includes an update on the size of the fire and response, what to expect from smoke, and the forecasted weather near the fire. Keep an eye out for them!

Air Pollution Forecast and Caution – A Primer

When air quality degrades to levels that are likely to affect your health the Department of Environmental Quality will announce this to the public using the Air Pollution Forecast and Caution tool. I'll drop an image below of what the announcements will look like. Look for these here, the DEQ Twitter account, and on our DEQ Facebook page.

An Air Pollution Forecast and Caution is a tool that the DEQ uses to let the public know that smoke concentrations have reached or are forecasted to reach and persist at levels likely to affect your health. The message will be posted on this blog There was a fairly lengthy period last summer that saw one region or another of the state with a Forecast and Caution issued or extended. One weekend in late August the entire state had been issued an Air Pollution Forecast and Caution.

The Forecast and Caution includes specific warnings and advice to those most likely to feel health impacts from smoke. It also prohibits intentional open burning on state and federal lands until the Forecast and Caution has been lifted. It is intended to help you make informed health decisions for the day AND limit further pollution buildup in the affected area. Use these along with your personal health history, the Air Quality Index, and visual observations to determine when to reduce or cancel your outdoor plans. 

Visual Observations and the Air Quality Index

Last week I mentioned that a lot of people use visual observations to gauge air quality. When sunlight encounters tiny pollution particles (in this case from smoke), it reduces the clarity and color of what we see. Sunlight is absorbed, shifted, or scattered when it hits these tiny pollution particles. As the amount of tiny pollution particles in the air increases (in this case from increasing amounts of smoke), the more the light is absorbed, shifted, or scattered and the hazier the sky will look.

While it’s still nice (not smoky anyway) go outside and pick a landmark that you know the distance of. Use this spot to help you figure out the AQI if you aren’t able to get it from any other media sources (perhaps you’re lucky enough to be enjoying yourself far from civilization and have no cell service or other way to access the google machine). So before you leave here, check out the chart below about using visibility to gauge the air quality and adjust your plans accordingly. Happy adventuring!

AQI Category	Visibility (miles)
Good	11+
Moderate	6-10
Unhealthy for Sensitive Groups	3-5
Unhealthy	1½  -2¾
Very Unhealthy	1-1¼
Hazardous	Less than 1

How do Treasure Valley residents perceive smoke?

Last summer, researchers at Boise State University did a survey of Treasure Valley residents about how they get their smoke information and how they feel about it. They presented the information to us at the end of the wildfire season and I think it would be helpful to share it with everyone out there as summer begins.

Wildfires have been on trend to get bigger and more damaging every year and as anyone in the West knows, fires come with massive amounts of smoke that disrupt our idyllic way of life here. The BSU researchers asked residents about their perception of the risk of wildfire smoke and their personal responses to the hazard. About 2/3 of respondents altered their outdoor activity plans based on forecasted smoke impacts. The majority of those that REDUCED their outdoor plans did so when air quality reached “orange” (unhealthy for sensitive groups) in the Air Quality Index. It took level “red” (unhealthy for all) before the majority would CANCEL outdoor plans.

Air quality information and their own visual observations were the most likely to get people to change their plans with text messaging and emergency alerts being the most likely way for them to get their information. Though the overwhelming majority believed wildfire smoke to be a hazard, most would not consider evacuating their home to avoid it. Medication, long showers, use of public buildings, and air filtration were the top choice for mitigating the effects of smoke.

Idaho Summer Wildfire Outlook

Summer is upon us! School is out. The weather is warm. The mountains and lakes are calling. For most of us here in Idaho, it’s time to live outside for a few months. So as you make your summer plans, you may be wondering what the wildfire potential is. Right now, the National Interagency Coordination Center is predicting wildfire season is looking “normal” with “above normal” potential in the Panhandle late in the summer. “Normal” doesn’t mean “no wildfires” – it means the “normal” amount of fires for this area is expected given the level of drought, amount of precipitation, and the fuel conditions in the region. So, a typical Idaho summer then.

NICC Predictive Services Outlook 6/10/2019