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• Timing of data collection and reporting:

  Times shown for data reports are the data collection start times and are always in Eastern Standard Time (EST). The time format is 24-hour military time.
  
  Example: A reporting time of 15:00 reflects the hourly average of the data that was collected starting at 3:00 p.m. EST and ending at 4:00 p.m. EST.

• What this means:
  If you look at the web page during the summer months when local time is on Eastern Daylight Savings Time (EDST) the data collection time shown can appear to be significantly delayed.
  
  Examples:
  
  If you look at the web page at 1:10 p.m. (13:10) local time (EDST) on June 15th, the most recent hour available on the web page would be 10:00 (EST). This would be the data that was collected from 10:00 to 11:00 (EST) or 11:00 to 12:00 (EDST). 
  
  If you go back to the site at 1:45 p.m. (13:45) local time (EDST) the most recent hour would be 11:00 (EST). This would be the data that was collected from 11:00 to 12:00 (EST) or 12:00 to 13:00 (EDST).    

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• How the data is collected:
  
  The data that is reported on this web page comes from continuous instruments that are constantly measuring their respective parameter at their location. Each air monitoring station has a data logger that reads the output of each instrument at the station once per second. At the beginning of the data collection start hour the 1-second readings are stored and used to create a 1-minute average. At the end of the hour the (60) 1-minute averages are averaged to create a 1-hour average for that parameter. It is this 1-hour average that is reported. This process is automatically repeated for each hour.

• How the data is retrieved and reported:
  
  The 1-hour averages are stored in the data logger until retrieved automatically by a central computer. Statewide data retrieval by the central computer begins shortly after start of each hour. Data for the previous hour is collected from each site, one at a time, and stored in the central computer database. This process is usually finished by quarter past each hour. The web site software can then update the data on the web page, which is usually completed by half past the hour.
  
  Note: The 8-hour average ozone data is the rolling average of the most recent 1-hour average plus the previous seven 1-hour averages. 

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