5.1 The reactivity and instability of O₃ precludes the storage of O₃ concentration standards for any practical length of time, and precludes direct certification of O₃ concentrations as SRM's. Moreover, there is no available SRM that can be readily and directly adapted to the generation of O₃ standards analogous to permeation devices and standard gas cylinders for sulfur dioxide and nitrogen oxides. Dynamic generation of O₃ concentrations is relatively easy with a source of ultraviolet (UV) radiation. However, accurately certifying an O₃ concentration as a primary standard requires assay of the concentration by a comprehensively specified analytical procedure, which must be performed every time a standard is needed.

5.2 The primary UV standard photometers, which are usually used at a fixed location under controlled conditions, are used to certify transfer standards that are then transported to the field sites where the ambient ozone monitors are being used. See Practice D5110.

5.3 The advantages of this procedure are:

5.3.1 All O₃ monitors in a given network or region may be traced to a single primary standard.

5.3.2 The primary standard is used at only one location, under controlled conditions.

5.3.3 Transfer standards are more rugged and more easily portable than primary standards.

5.3.4 Transfer standards may be used to intercompare various primary standards.

1.1 These practices describe means for calibrating ambient, workplace or indoor ozone monitors, using transfer standards.

1.2 These practices describe five types of transfer standards:

Practice A—Analytical instruments,

Practice B—Boric acid potassium iodide (BAKI) manual analytical procedure,

Practice C—Gas phase titration with excess nitric oxide,

Practice D—Gas phase titration with excess ozone, and

Practice E—Ozone generator device.

1.3 These practices describe procedures to establish the authority of transfer standards: qualification, certification, and periodic recertification.

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. See Section 8 for specific precautionary statements.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.