Note: - TNMHC is total non-methane hydrocarbons, AIRS parameter code 43102. - Targeted compounds are the 55 volatile organic compunds individually measured at PAMS stations. - Time is daylight saving time. - ppbC is parts per billion carbon. - Morning hours (6-9 a.m.) are used because the daily ozone reaction cycle has not begun to convert the VOCs to ozone.

Source: Mark Schmidt of EPA prepared this chart based on data in the AIRS system.