Thermo Scientific 49iQ, Instruction Manual

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Thermo Scientific 49iQ Instruction Manual 4-1
Chapter 4
Calibration
This chapter describes how to perform a multipoint calibration of the
photometric ozone analyzer. It is based upon the current EPA approved
procedure using a UV photometer as a calibration standard. The
information described here should be adequate to perform the calibration.
However, for more information refer to the Code of Federal Regulations
(Title 40, Part 50, Appendix D) and the EPA's “Technical Assistance
Document for the Calibration of Ambient Ozone Monitors.”
The following equipment is required to calibrate the instrument:
●
Zero air generator
●
Calibration photometer system
Zero air can be obtained either from compressed cylinders or from
scrubbed ambient air. If cylinder air is used, it should be actual and not
synthetic. If ambient air is used, the following compounds must be
removed: ozone, nitric oxide, nitrogen dioxide, sulfur dioxide, and
hydrocarbons. The following scheme is recommended by the EPA in its
technical assistance document:
1. Irradiate the air with an ozone generating UV lamp to convert nitric
oxide to nitrogen dioxide. Alternatively, pass air through Purafil® which
oxidizes nitric oxide to nitrogen dioxide and scrubs nitrogen dioxide.
2. Pass air through a large column of activated charcoal to remove residual
nitrogen dioxide, ozone, sulfur dioxide, hydrocarbons, and so on.
3. Pass air through a molecular sieve.
4. Pass air through a final particulate filter to remove particulates which
originate in scrubbing columns.
Equipment Required
Zero Air Generator