ASI/TRACEGAS/M1 - Slow return to ambient measurement after HNO3 calibration

Nitric acid permeation source is used to calibrate at 06:00 on odd days.  The response on 
the NO2 and NOy channels is large and takes excessive time to recover after the 
calibration.  This is apparent as a spike in the data after the calibration.  Users should ignore 
this spike.  HNO3 calibration was turned off.

The return to ambient can be as long as an hour or more.

• One minute average of NOx values(nox)
• One minute average of NOy values using nominal sensitivity correction and
  nominal Mo converter efficiency(noy)
• One minute average of NO2 values calculated with nominal sensitivity correction
  and nominal BLC efficiency(no2)