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Air Quality Index

Air Quality Index

The U. S. Environmental Protection Agency (EPA) has provided a scale called the Air Quality Index (AQI) for rating air quality. This scale is based on the National Ambient Air Quality Standards (NAAQS) and is described in the Code of Federal Regulations, Part 58, Appendix G. This report is based on the AQI standards. More information on the AQI can be found on the EPA's AirNow web site.

Reporting for August 18, 2017 as of 10:11 pm MST                  
Metropolitan Area
or
Non-Metropolitan County
Air Quality RatingCritical
Pollutant
Air Quality Index
OzoneCarbon MonoxideSulfur DioxidePM-10
(Std Cond)
PM-2.5
(Lcl Acpt)
PM-2.5
(Lcl Cond)
1-Hour8-Hour8-Hour1-Hour24-Hour (2)24-Hour (2)24-Hour (2)
AQIppbAQIppbAQIppmAQIppbAQIµg/m³ (25° C)AQIµg/m³ LCAQIµg/m³ LC
CT-ME-MA-NH-RI-VT -- Region 1
Penobscot (1)     §§  §                   
Pleasant Point Good Ozone * 32 19 23                    
NJ-NY-PR-VI -- Region 2
St Regis (1) Good PM-2.5 * 4 3 3       §§    49 11.79    
KY-TN-NC-SC-MS-AL-GA-FL -- Region 4
Cherokee (1)     §§  §                  §
MT-ND-WY-SD-UT-CO -- Region 8
Polson-Ronan (1)                     §       
CA-NV-AZ-HI-AS-GU -- Region 9
Bishop Good Ozone * 30 21 25                    
Fort Independence Good PM-10                 13 14.07        
Fort McDowell Good Ozone * 70 50 59         26 27.87        
Las Vegas (1) Good PM-10   §§  §        7 7.06     6 1.38
Lone Pine Good PM-10                 13 14.03        
Pyramid Lake Good PM-10                 33 35.23        
Reno/Sparks (1) Hazardous PM-2.5                   §    500 984.86
Walker River (1)                     §       
Williams Good PM-2.5 * 0   §                 39 9.40
Yerington (1)                     §       
WA-OR-ID-AK -- Region 10
Coos Bay (1)                         §   
Fort Hall Good PM-2.5                 31 33.49     36 8.60
Kamiah Good PM-2.5                     38 9.20    
Lapwai Good PM-2.5                     17 4.05    
Reubens Good PM-2.5                     ## -0.01    
Warm Springs (1)                         §   
The highest AQI value and associated average (1-hour, 8-hour, or 24-hour) that is responsible for the AQI rating are highlighted bold in the table.
PM-10 is measured at standard pressure and temperature conditions.
PM-2.5 is measured at local pressure and temperature conditions.
(1) - Not all monitors are reporting for this metropolitan area.
(2) - This is an average since midnight for the current day and does not represent an entire day of data.
The reported overall AQI category could change and will not be complete until all the data for the calendar day is polled and processed and could be further subject to later change by the data validation process.
† - No AQI has been calculated for this metropolitan area. This can happen early in the morning before enough valid ozone or carbon monoxide hourly samples have been collected to create an eight-hour average and should clear up once enough samples are collected.
If there are no measurements for any parameter this may indicate a data collection problem. Once any data collection problem is resolved, the data will be filled in and an AQI will be calculated (if possible).
§ - No data of this type was collected on August 18, 2017 for this metropolitan area, or there were not enough valid hourly samples collected on this date to meet data completeness requirements of a minimum of 18 valid hourly samples in a day,
or there have not been enough valid ozone or carbon monoxide hourly samples collected to create an eight-hour average.
§§ - There have been no hourly averages of this parameter collected for August 18, 2017 in this metropolitan area.
* - There is no AQI associated with hourly ozone averages less than 0.125 ppm (125 ppb).
## - No AQI is defined for negative values.

PLEASE NOTE:  Data in this table is collected from TREX air monitoring sites, local agencies, and private monitoring networks. Site specific information is available for each metropolitan area by clicking on the metropolitan area name. This data has not been verified by the TREX or the responsible entity and may change. While this is the most current data, it is not official until it has been certified by the appropriate technical staff. This table is updated hourly. Click here for information about all the monitoring sites.

The table above lists the current peak concentration for the critical pollutant, the corresponding Air Quality Index (AQI) category, and the AQI ratings for each of the NAAQS pollutants that are measured real-time. The critical pollutant is the pollutant with the highest AQI rating measured in the area. The table is updated each hour and covers the period from midnight through the indicated ending time for today's data or from midnight to midnight on other days. Listings are provided for each metropolitan area where pollutant levels are monitored by TREX.

Interpreting the AQI

Air Quality Index

Each NAAQS pollutant has a separate AQI scale, with an AQI rating of 100 corresponding to the concentration of the Federal Standard for that pollutant. Additional information about the AQI and how it can be used is available from the EPA's AirNow web site.

Place your mouse pointer over the scale displayed above to view information about the Air Quality Index, and each of the rating levels.

The actual index calculation is different for each parameter measured and is specified by the EPA. The following table shows the various breakpoints used in calculating the AQI.

AQI Breakpoint Definitions
AQI Range 1hr Ozone
in ppm
8hr Ozone
in ppm
8hr Carbon Monoxide
in ppm
1hr Sulfur Dioxide
in ppm
24hr Sulfur Dioxide
in ppm
24hr PM-10
in µg/m³ (25° C)
24hr PM-2.5
in µg/m³ LC
24hr PM-2.5
in µg/m³ LC
0 - 50 Not Defined 0 - 0.059 0 - 4.4 0 - 0.035 Not Defined 0 - 54 0 - 12 0 - 12
51 - 100 Not Defined 0.06 - 0.075 4.5 - 9.4 0.036 - 0.075 Not Defined 55 - 154 12.1 - 35.4 12.1 - 35.4
101 - 150 0.125 - 0.164 0.076 - 0.095 9.5 - 12.4 0.076 - 0.185 Not Defined 155 - 254 35.5 - 65.4 35.5 - 55.4
151 - 200 0.165 - 0.204 0.096 - 0.115 12.5 - 15.4 0.186 - 0.304 Not Defined 255 - 354 65.5 - 150.4 55.5 - 150.4
201 - 300 0.205 - 0.404 0.116 - 0.374 15.5 - 30.4 Not Defined 0.305 - 0.604 355 - 424 150.5 - 250.4 150.5 - 250.4
301 - 400 0.405 - 0.504 Not Defined 30.5 - 40.4 Not Defined 0.605 - 0.804 425 - 504 250.5 - 350.4 250.5 - 350.4
401 - 500 0.505 - 0.604 Not Defined 40.5 - 50.4 Not Defined 0.805 - 1.004 505 - 604 350.5 - 500.4 350.5 - 500.4
500+ Not Defined Not Defined Not Defined Not Defined Not Defined 605 - 4999 500.5 - 999.9 500.5 - 999.9

PLEASE NOTE: This data has not been verified by the TREX and may change. This is the most current data, but it is not official until it has been certified by our technical staff. Data is collected from TREX ambient monitoring sites and may include data collected by other outside agencies. This data is updated hourly. All times shown are in local standard time unless otherwise indicated.