However, it should be noted that ETS contains data for a limited number and type of facilities and therefore cannot be used to estimate overall SO2, NOx or CO2 emissions for a geographical area. For most units, a Continuous Emissions Monitoring system must be used to analyze and record data at least every fifteen minutes. All emissions and flow data are aggregated to one hour averages which are reported to the Emissions Tracking System on a quarterly basis. Data are maintained on a historical basis, allowing for temporal analysis. These estimates are derived from fuel type and consumption of operating units.
All sites collect information on the same variables using identical collection parameters.
As units are retired, their monitoring periods cease, and as units come online, new records are added to the database. Records from the 400 units that have been retired since the inception of the program are still maintained in the database. The data contained within ETS have the potential to be linked with data from other sources. ETS data may be linked through unit addresses and ZIP code. Latitude and longitude of units are not collected for submission to the ETS database.