This is our 25th annual data summary, which reviews air quality and meteorological data for the Puget Sound Region. This year's report marks the end of a quarter century of air monitoring and tremendous strides in improving air quality in the Puget Sound region. It also marks the beginning of a new era in monitoring responsibilities as a result of new federal standards for fine particulate matter. Fulfilling these requirements will challenge the agency to evolve our existing monitoring network to accurately depict fine particulate pollution levels impacting our neighborhoods and regional visibility.
    It also marks the beginning of a new look for the presentation of air quality data. This executive summary and its pollutant- specific companion pages highlight the most important data for the previous year. More technical air quality data is available on the agency's web site at www.psapca.org. Specialized data packages can be ordered directly from us.
   Air Quality Summary for 1996
   For the sixth consecutive year, we recorded no violations of any National Ambient Air Quality Standards (NAAQS). Good air quality conditions prevailed throughout 1996 with no days of unhealthy air measured on the daily Pollutant Standards Index. Brief periods of elevated air pollution levels are summarized by pollutant:
    Carbon Monoxide (CO). The highest recorded 8-hour average was measured at 8.7 ppm on October 9, 1996 at both the University District and downtown Seattle (5th and James St.) monitoring stations. While these values accurately reflect real conditions, they occurred during an unusually warm weather pattern not normally associated with cold air stagnation that traps and elevates carbon monoxide values.
   The Department of Ecology's Northwest Regional Office conducted a special study of carbon monoxide in the vicinity of

Sea-Tac International Airport and the surrounding communities. This study did not identify any hot spots or exceedances of the ambient air quality standards.
   Attainment continues to be demonstrated across the Puget Sound region CO monitoring network.
    Particulate Matter (PM10 and PM2.5). Attainment of the PM10 standard was again demonstrated throughout the Puget Sound region in 1996. In February, an air stagnation resulted in a brief period of impaired air quality. During this period, 24-hour PM10 values exceeded the Washington State "imaired air" or "burn ban" trigger of 75 ug/m3, but remained well below the federal standard. The agency issued a first stage burn ban for King, Pierce and Snohomish counties. Although a significant portion of the particulate matter was believed to be road dust as a result of winter road sanding, the burn ban was called to reduce the wood smoke contribution to total particulate matter pollution. Record rain and snowfall from winter storms prevailed during much of November and December, making that period of our traditional wood smoke season uneventful. During the winter the agency and Ecology's Northwest Regional Office initiated a joint particulate matter pollution survey in the Issaquah area. The purpose of the survey was to determine if pollution levels in Issaquah are higher than those detected at other monitoring sites, and if so, locate any hot spots for particulate matter pollution. This project was a milestone in air monitoring for the agency's Technical Services department. Staff members established two stationary monitoring sites and performed nighttime mobile nephelometer monitoring during periods when temperature inversions were trapping pollutants. Preliminary results of the survey show that PM10 values were lower than at other