National Park Service

Air Resources






For more information about National Park Service air resources, please visit http://www.nature.nps.gov/air/.

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Ozone Standard Exceedances in National Parks

Map of 2011 Ozone Exceedances (Click photo to enlarge)

The National Park Service (NPS) actively monitors ozone at its parks from April to October. Ozone measurements are compared with the National Ambient Air Quality Standard (NAAQS) for ozone. The Environmental Protection Agency (EPA) sets this standard as the level at which the ozone in the air becomes unhealthy.

The NPS tracks the days when the standard is exceeded in the parks. The table below displays the parks and the ozone values along with the number of days when the daily maximum 8-hour average ozone concentration exceeded the standard of 75 parts per billion (ppb)†. The fourth highest ozone column has been color-coded for easier viewing. The thumbnail on the right links to a map of parks with 2011 ozone exceedances.

2011 Ozone Standard Exceedances
National Park April May June July Aug. Sept. Oct. 2011 Season
Total Count Max 8-hr O3 (ppb) 4th highest max.
8-hr O3 (ppb)
Acadia– Cadillac Mountain 0 0 1 1 0 0 0 2 92 74
Big Bend– K-Bar Ranch Road 4 0 3 0 0 0 0 7 86 80
Carlsbad Caverns– Maintenance Area 0 1 0 0 0 0 0 1 76 70
Chamizal– State Monitor 0 0 2 0 1 0 0 3 82 70
Chiricahua– Entrance Station 0 0 0 0 1 0 0 1 76 75
Cowpens– State Monitor 0 0 1 0 0 0 0 1 77 71
Death Valley– Park Village 0 0 3 0 0 0 0 3 79 75
Grand Canyon– The Abyss 0 2 0 0 0 0 0 2 78 74
Great Smoky Mountains– Cades Cove 0 0 0 1 0 0 0 1 98 68
Great Smoky Mountains– Clingman's Dome 0 0 2 0 0 2 0 4 86 79
Great Smoky Mountains– Cove Mountain 0 0 6 1 0 1 0 8 86 78
Great Smoky Mountains– Look Rock 0 0 5 3 3 1 0 12 87 83
Great Smoky Mountains– Purchase Knob 0 0 1 0 0 0 0 1 77 67
Joshua Tree– Black Rock 3 8 12 12 14 6 1 56 104 91
Joshua Tree– Cottonwood Canyon 0 1 1 3 0 0 0 5 78 76
Joshua Tree– Pinto Wells 0 1 3 0 0 0 0 4 78 76
Kings Mountain– Brown's Mountain 0 0 2 0 0 0 0 2 88 74
Little River Canyon– Canyon High 0 0 0 0 0 1 0 1 81 66
Mammoth Cave– Houchin Meadow 0 0 0 0 0 0 0 0 73 71
Mesa Verde– Resource Management Area 0 0 0 1 0 0 0 1 78 70
Mojave– Kelso Mountains 0 2 4 0 0 0 0 6 80 78
Pinnacles– SW of East Entrance Stn. 0 0 0 0 0 0 0 0 73 69
Rocky Mountain– Long's Peak 0 2 2 3 1 0 0 8 80 77
Saguaro– Pima County 0 1 0 2 0 0 0 3 80 75
Sequoia and Kings Canyon– Ash Mountain 0 2 15 22 29 19 0 87 103 98
Sequoia and Kings Canyon– Lower Kaweah 0 0 7 10 10 4 0 31 84 81
Shenendoah– Big Meadows 0 0 0 2 0 0 0 2 76 72
Yosemite– Mobile 0 0 0 0 1 1 0 2 79 72
Yosemite– Turtleback Dome 0 0 2 2 1 3 0 8 84 79

Validation Level *

2

2

2

2

2

2

2

 

 

 

*Validation level 0 indicates raw data. Validation level 1 indicates preliminary data. Validation level 2 indicates final, validated data. Counts of days with 8-hr average ozone greater than 75 ppb may change after the data is fully validated. The ozone season runs from April to October for the detailed current ozone conditions. During the winter, more limited numbers of locations and web products are available.
†The current NAAQS is 75 ppb, daily maximum 8-hour average. The ozone standard is violated when the 3-year average of the annual fourth-highest daily maximum 8-hour average ozone concentration is greater than 75 ppb, which occurs when the 3-year average exceeds 75 ppb. An exceedance occurs when the daily maximum 8-hour average is greater than 75 ppb.

Annual Exceedance Summaries

2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004

2003 (pdf, 137 KB) | 2002 (pdf, 146 KB) | 2001 (pdf, 136 KB) | 2000 (pdf, 133 KB)

Compiled Exceedance Summaries

Last Updated: June 20, 2012