+Air Quality Index (AQI)
Don's Home Health | California Fires Air Quality Index (AQI)
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Contents: About | AQI Reports | Reference - Sources
Air Quality Index Levels of Health Concern Numerical
Value
Breakpoints
µg/m3 *
Lung Association Advisory
Good 0 to 500 -12.0 Air quality is satisfactory, and air pollution poses little or no risk. None
Moderate 51 to 10012.1-35.4 Air quality is acceptable; However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution. Unusually sensitive individuals should consider limiting prolonged outdoor exertion
Unhealthy for Sensitive Groups 101 to 15035.5-55.4 Members of sensitive groups may experience health effects. The general public is less likely to be affected. Children, active adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion
Unhealthy 151 to 20055.5-150.4 Some members of the general public may experience health effects; Members of sensitive groups may experience more serious health effects. Children, active adults, and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion.; everyone else should limit prolonged outdoor exertion
Very Unhealthy 201 to 300150.5-250.4 Health alert: The risk of health effects is increased for everyone. Children, active adults, and people with respiratory disease, such as asthma, should avoid outdoor exertion.; everyone else should limit outdoor exertion
Hazardous 301 to 400250.5-350.4 Health warning of emergency conditions: Everyone is more likely to be affected. Everyone should avoid all physical activity outdoors
401-500350.5-500

Note: Values above 500 are considered Beyond the AQI. Follow recommendations for the "Hazardous category."
Additional information on reducing exposure to extremely high levels of particle pollution is available at the EPA.

* µg/m3- 24- hour fine particle standard in micrograms per cubic meter.

The National Ambient Air Quality Standards for Particle Pollution REVISED AIR QUALITY STANDARDS FOR PARTICLE POLLUTION AND UPDATES TO THE AIR QUALITY INDEX (AQI)

AQI reporting vales vary by the sensor used.
See AQI Measurement

Air Quality Index (AQI) Basics An AQI value is computed for each pollutant (ground-level ozone, particle pollution, carbon monoxide, and sulfur dioxide) using standard formulas developed by EPA. The highest of these AQI values is reported as the AQI value for that day.
AQI today and tomorrow for your location | EPA AirNow.gov
AirNow - How is the NowCast algorithm used to report current air quality?

Air Quality Index - A Guide to Air Quality and Your Health


Data Sources - Reports:
California Air Quality Index (AQI) | IqAir
N. Central California | PurpleAir.com | Davis | Homewood
It gives a 6 day forecast and ozone in addition to PM2.5

With Forecast:
AirNow.gov is a partnership of the EPA, NOAA and several other agencies to provide AQI information
Accuweather

Sensors:
Accuweather Plume Labs
AirNow (EPA)
The AirNow site displays hourly, not real-time, readings. 
Fire and Smoke Map EPA

Purple Air 
 The data comes from the commercial sensors the company sells,
 which members of the public install on porches, yards and
 other neighborhood sites.  
Sensors are less accurate than AirNow
You can click on "standard" in the box at the bottom
to get a conversion to match other AQI systems.
Discrepencies in reports:
From PurpleAir to AirNow, Your Air Quality Maps for Wildfire Smoke | KQED
Users have noticed a discrepancy between what official sites are reporting and the readings displayed on PurpleAir.
Web Cams:
Westshore Cafe
Fire Camera Displays | Nevada Seismological Lab

Examples:
On September 14th 2020 Air quality hit 503 as measured by Purple Air near the California Oregon border.
AQI reporting vales vary by the sensor and parameters used.
See AQI Measurement
E.g. on August 23 2021 AQI at Tahoe City was reported as:
 Purple Air - 770-957
 AirNow (EPA)- 566
 AccuWeather - 138
Anything over 300 is considered hazardous by the EPA and their scale doesn't go above 500
This was the average over several hours so was not a 10 minute spike. click on image to enlarge

I left my car windows open a crack because of the 108° temperature and it was covered with ash from the fires in the morning.


The next day the smoke was blown east to the Sierra Nevada and air quality hit 573 at Mammoth Lakes North-East of the Creek fire.
A day later the air quality averaged 740 over a 2 hour period near Shaver Lake at the edge of the Creek Fire.


Terms:
AQ&U

AQI

CF_ATM

CF_1

LRAPA

PM - Airborne particulate matter (PM) is not a single pollutant, but rather is a mixture of many chemical species. It is a complex mixture of solids and aerosols composed of small droplets of liquid, dry solid fragments, and solid cores with liquid coatings. Particles vary widely in size, shape and chemical composition, and may contain inorganic ions, metallic compounds, elemental carbon, organic compounds, and compounds from the earth’s crust.
Particles are defined by their diameter for air quality regulatory purposes. Those with a diameter of 10 microns or less (PM10) are inhalable into the lungs and can induce adverse health effects. Fine particulate matter is defined as particles that are 2.5 microns or less in diameter (PM2.5).
World Health Organization considers PM2.5 the world’s single biggest environmental health risk.

Particulate matter(PM) is the primary pollutant in the US. PM comes in many different sizes and it can as small as a hair. 90% of the time particulate matter is inviable to human eyes. PM has many sources, such as combustion such burning fuels from cars, ships, airplanes, trucks, buses. Also, it comes from certain types of facilities as cooking facilities, meat industries, wood-burning, wildfires. PM also comes from natural resources like dust and storms. But most of the PM in the is formed by a mix of several pollutants retained in the air.

Indoor PM2.5 levels can be influenced by outdoor sources like vehicle exhaust, wildfires, and power plant emissions.
See:
Inhalable Particulate Matter and Health (PM2.5 and PM10) | California Air Resources Board
Measuring Instruments for Indoor Environmental Quality

PM2.5 - 2.5 micron or less particle
PM10 - 10 micron or less particle

µg/m3 24- hour fine particle standard in micrograms per cubic meter.


Links - Sources:
Air Quality 101 | North Carolina Department of Environmental Quality
The National Ambient Air Quality Standards for Particle Pollution REVISED AIR QUALITY STANDARDS FOR PARTICLE POLLUTION AND UPDATES TO THE AIR QUALITY INDEX (AQI) | EPA
last updated 22 Aug 2020