Yosemite National Park: Air Quality 10-day ChartsParticulate Matter (PM2.5) Data Collected at the Yosemite Valley Visitor Center Monitoring Site
Operated by the California Air Resources Board
Particulate Matter Less Than 2.5 Micrometers in Diameter (PM2.5): 1-hour and 24-hour average concentrations
The chart below plots both the 1-hour and running 24-hour average PM2.5 concentration, but only the 24-hour average should be used to compare with the standard. The standard is exceeded when the 24-hour concentrations go above 35 micrograms per cubic meter, as denoted by the line with the label NAT'L AMBIENT AIR QUALITY STANDARD. The background of the chart is color coded and relates to the EPA National Ambient Air Quality Standard for particulate matter, which is designed to protect human health.