Before and After



Rogues Gallery

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Bad NO2

Free Calibration Spreadsheet


 Before and After


Here are a few examples showing the raw unscaled data (15-minutes) and then the final processed concentrations (hourly).

Does your final data look this good?

I can help you clean up your data.

Calculating the concentrations from the raw data and eliminating bad data is the very essence of air quality data processing. Making the final dataset look good can become difficult if you do not understand how instruments and calibrations can go wrong. Applying the correct sensitivity, ramping between calibrations, correcting for NOx converter inefficiencies and using stable certified gas standards is another topic all together.


Large NO baseline offset, a calibration peak in June and a step change in August.

NO, NOx and NO2

NO and NOx instrument channels show regular auto-calibrations peaks and then baseline instability.

The NO2 instrument channel should always be ignored!


The after plots show the cleaned up NO and NO2 ppb concentrations.


Regular ozone auto-calibration spans showing in the data.


Internal sampling between LSO visits


Large baseline offset, zero spikes and roller coaster baseline.


TEOM instruments can show random down spikes and long periods of symmetrical noise.

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