AQ Monitoring Results:
Crockett: Carbon Monoxide at John Swett

This page last reviewed September 27, 2010


Carbon monoxide (CO) is a colorless and odorless gas at room temperature. Carbon monoxide is readily absorbed through the lungs into the blood, causing insufficient oxygen to reach the heart, brain, and other tissues. The resultant harm can be critical for people with heart disease, chronic lung diseases, and anemia, as well as for unborn children, especially at high elevations where the air is less dense.

Carbon monoxide is formed as a result of incomplete combustion of fuels and waste materials such as gasoline, diesel fuel, wood and agricultural debris. Mobile sources generate over 85% of the CO emissions in California. Industrial sources are small, due in part to the widespread use of natural gas as a fuel and the presence of combustion controls. Natural sources of CO include biomass burning, soil biological processes, releases from vegetation and termites, and releases from the ocean.

Both the national and state standards for CO have been established to protect the public health. The standards establish the concentrations above which CO is known to cause adverse health effects in humans. The current standards are:

State CO Standards:
20 ppm* for 1 hour
9 ppm for 8 hours
6 ppm for 8 hours for Lake Tahoe Air Basin only
National CO Standards:
35 ppm for 1 hour
9 ppm for 8 hours

*ppm means parts per million.

Currently, CO levels in most areas of California are below both the national and state standards, except in Los Angeles County and the city of Calexico. Much of the progress in reducing ambient CO is attributable to motor vehicle controls and the introduction of cleaner fuels.

Ambient Monitoring Results

Ambient levels of CO are monitored hourly at approximately 100 sites in the California ambient air quality measurement network. Based on the standards, the 1-hour and 8-hour average concentrations are used to determine the ambient CO levels. Daily maximum of 8-hour CO measurements is a useful parameter to indicate the CO levels. During year 1998 through 2000, the statewide average concentration of daily maximum of 8-hour CO measurements was 1.2 ppm (parts per million). Relative to the statewide average, the region surrounding Crockett was 30% lower with an average concentration of 0.85 ppm for the same time period.

The ambient monitoring results at John Swett are provided here:

  • A graph comparing the monthly summaries of carbon monoxide at the community with historical statewide and regional levels
  • A table of summary statistics
  • Raw data in Excel format