Overview
ISO 13964:1998/Amd 1:2024 is an amendment to ISO 13964 (Ultraviolet photometric method) that provides a consensus value for the ozone absorption cross‑section at room temperature for the mercury-line wavelength 253.65 nm (air). The amendment updates numeric constants, formula parameters and bibliographic references used in the UV photometric determination of ozone in ambient air to reflect current metrological consensus and improved accuracy.
Key topics and technical changes
- Consensus absorption value: The amendment updates the ozone absorption cross‑section value used in the standard (change from “1,44” to 1.4214 as shown in the revised formulas).
- Precise wavelength: Mercury line wavelength corrected from 253.7 nm → 253.65 nm (air) throughout the document and formulas.
- Reference pressure: Numerical reference pressure adjusted from 101,25 → 101.325 in relevant clauses and formulas.
- Editorial corrections: Minor editorial changes such as changing “back‑pressure” to “backpressure” and standardized numeric presentation in formulas (Formulas (1)–(3) and clause updates).
- Updated references: Reference [3] replaced by the 2019 Metrologia literature review recommending the consensus value; a BIPM 2022 report on units, significant digits and rounding for the 253.65 nm cross‑section is added as Reference [16].
- Affected clauses: Revisions applied to Clause 1, Clause 3, Clauses 5.1/5.2, 7.1/7.2, and the bibliography.
Practical applications and users
This amendment is directly relevant to:
- Ambient air quality monitoring networks - ensures consistent ozone concentration results across sites using UV photometry.
- Analytical and environmental laboratories - required for correct instrument calibration and data reporting.
- Instrument manufacturers and calibrators - must implement the updated constants and formula inputs in firmware, calibration routines and manuals.
- Regulators and compliance bodies - benefit from harmonized, metrologically‑traceable ozone measurements for standards and legislation.
- Metrologists and standards developers - for applying appropriate significant digits, units and rounding rules per the BIPM recommendation.
Practical steps for implementers:
- Update instrument calibration factors and software to use 253.65 nm and 1.4214 where specified.
- Review formulas and documentation that reference the previous numeric values (Formulas (1)–(3) and clauses noted in the amendment).
- Consult the cited Metrologia (2019) review and BIPM (2022) report for guidance on units, significant digits and rounding.
Related standards
- ISO 13964:1998 (base standard) - UV photometric method for ozone in ambient air.
- Metrology and reporting guidance (BIPM/Metrologia reports referenced in the amendment) for traceability and numeric presentation.
Keywords: ISO 13964:1998/Amd 1:2024, ozone absorption cross-section, 253.65 nm, ultraviolet photometric method, air quality monitoring, calibration, metrology.