Model 405 nm NO
2
/NO/NO
x
Monitor Manual Rev. D
26
Zero air can be generated either from compressed cylinders or from scrubbed ambient
air. If ambient air is used, contaminants such as nitrogen dioxide and nitric oxide must
be removed. The Model 405 nm will perform better if the zero air has humidity in the
range 10-90 %RH. A set of DewLine
TM
Nafion tubing is included with the Model 405
nm for installation between a dry gas supply and the instrument. The DewLine
TM
Nafion tubing introduces humidity to dry air or calibration standards without loss of
NO
2
or NO.
7.1.2. Setup Check
A visual inspection of the calibration setup should be performed before performing a
calibration to verify that the setup is in proper order. All plumbing connections should
be checked. Any obvious leaks should be fixed and the sampling tee and sampling
lines should be checked for general cleanliness. For more information, refer to the
manufacturer's User Manual for the calibrator.
7.2. Calibration Procedure
A multipoint calibration should be performed at least every 12 months. Within this
calibration frequency, a multipoint calibration is advised whenever major disassembly
of components is performed, or any time the zero or span checks give results outside
of the acceptable limits.
7.2.1. Instrument Preparation
1. Turn on the Model 405 nm and allow it to stabilize for a minimum of one
hour.
2. Enter the calibration menu (Main Menu /Cfg / Cal) and set the zero values
to 0 and the slope values to 1.00 for both NO
2
and NO.
3.
Connect the monitor to a sampling tee from the calibrator. The outlet of the
calibrator must be vented to atmosphere so that pressure does not build up
in the setup. Connection of the Model 405 nm directly to a pressurized
output of any device can damage the monitor.
4. Verify that there is an overflow at the vent of the sampling tee.
Model 405 nm
Nitric Oxide
Cylinder
Zero Air
Supply
Vent
NO
2
, NO
Calibrator
