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Passive Ozone Sampler Monitoring Program


A typical passive sampling site. The samplers are in the cups at the top pf the pvc pole. Zion National Park, Utah
Passive ozone samplers provide a low-cost alternative for the monitoring of ozone on a weekly basis. The samplers require no power, have a simple deployment system, and take only a few minutes each week to exchange samplers. Their main uses are in determining trends, getting base-line conditions, and for mapping distributions of ozone over space.


US Map of passive sampler locations

A passive sampler device

This low cost alternative for ozone monitoring, passive ozone samplers, was studied extensively prior to initiation of a routine monitoring network using the devices. Weekly ozone doses are measured in the parks highlighted on the map.

A list of parks where passive ozone samplers have been used, is available.


The ozone analyzers have been used for specialized studies at:

  • Great Smoky Mountains NP - massive volunteer study of spatial O3 distribution, GIS mapping and models
  • Great Smoky Mountains NP - for ozone injury coneflower studies
  • Joshua Tree NP - spatial distribution of ozone, seasonal changes, comparison to existing monitoring
  • Mount Rainier NP - spatial distribution and monitoring at vegetation injury plots
  • Seqouia-Kings Canyon NP - spatial distribution of ozone
  • Yosemite NP - spatial and vertical elevation distributions of ozone


The field procedures for the passive ozone sampling are given in the standard operating procedures and documents below. The lab procedures can be obtained from Ogawa.

  • Suggestions on design of a passive ozone monitoring study design: Passive Sampling Study Design (PDF)
  • AWMA Air Toxics and Related Air Pollutants symposium presentation (PDF) with preliminary study results on the Ogawa passive samplers.
  • Overview article of some results and a discussion of operations using the passive samples for ozone monitoring within the National Parks. PDF, 290 kb or version (PDF, 160kb) that includes estimates of costs.
  • Journal article on NPS use of ozone passive samples, Spatial Distribution of Tropospheric Ozone in National Parks of California: Interpretation of Passive-Sampler Data, John D. Ray, The ScientificWorld (2001) 1, 483-497. View abstract. Request reprint from the author.
  • Other articles from the International Symposium on Passive Sampling of Gaseous Air Pollutants in Ecological Effects Research, 2001, Riverside, CA. Symposium abstracts.
  • Field operations Standard Operating Procedures for 2003 - field operations, list of parks, table of blanks and duplicates per month, sampler coding information (PDF)


Results from the passive sampling program are used to determine baseline ozone values, look for trends, estimate peak seasonal ozone values, fill in spatial characterizations of ozone, and to provide supporting data for vegetation injury studies.
For a comprehensive overview of all the sites in the Passive Ozone program, including the monitoring start and end dates and locations in latitude and longitude, please see our site list (Excel format, 51kb). This site list is different from the Locations site list, which primarily shows what year passive ozone monitoring was done at the parks.
Tables of ozone concentration data expressed as weekly average ozone in ppb are available below:

map icon
2005 X Data Annual Map
2004 X Data Annual Map
2003 page 1
page 2
Data Annual Map
2002 page 1
page 2
Data Annual Map
2001 X Data Annual Map
2000 X Data Annual Map
1999 X   Annual Map
1998 X   Annual Map
1997 X   Annual Map
1996 X   Annual Map
1995 X   Annual Map

Also available is the summary report on ozone monitoring using passive samplers ..... 1995-1996 draft (PDF 640 kb) and the data appendix (PDF 250 kb)

Spatial Distribution Studies

Several special studies have been done with ozone passive samplers to assess the representatives of ozone monitoring in complex terrain. Some samples are posted below and in the draft report and presentations above.

sample map of ozone distribution in Great Smoky Mtns NP
Red areas have the highest ozone during the summer at Great Smoky Mountains National Park.


Great Smoky Mountains National Park, summer 2000 ozone distribution special study web site and results. A large number of volunteers helped by doing the field portion of the passive sampler study.The red areas in the map of the park show where the seasonal average ozone is highest. These areas are mostly the higher elevation locations.

Also available is a poster about the study.

Ozone interpolation map using
   passive and continuous monitor data.


Map of Ozone Monitoring Sites in Southwest US


The ozone passive sampler data fills in information on baseline concentrations for a number of Class I areas that would not have gotten any ozone monitoring otherwise. The map to the right estimates the seasonal average ozone over a portion of the western US. Rural monitoring sites in the southwest have higher ozone than the northern areas of the western US.




The ozone passive sampling program is run on a tiny budget with the assistance of the Air Resources Division, in-park staff, and the NPS monitoring network support contractor. For information, to join in the monitoring effort, or to suggest additional uses for the passive samplers, please contact:Dr. John D. Ray, program manager - (NPS-ARD) (303)969-2820

Contractors: These are the contractors and suppliers for the NPS ozone passive sampling program. [Not an endorsement]

RTI does all the sample handling and lab analysis
  • Air Resource Specialists (ARS), John Faust - (970) 484-7941

ARS is the field support contractor - they provide rainshields, support tees, monitoring assistance, and the database archive. http://www.air-resource.com/air-quality.php


Spatial Distribution of Tropospheric Ozone in National Parks of California: Interpretation of Passive-Sampler Data, John D. Ray, The ScientificWorld (2001) 1, 483-497. View abstract. Request reprint from the author.

Ogawa USA is the source for the passive sampler devices. http://ogawausa.com/passive.htm

  • Ogawa & Co., USA, Inc. - Don Schaeffer - (954) 781-6223
updated on 01/17/2007  I   http://nature.nps.gov/air/Studies/passives.cfm   I  Email: Webmaster