Following the CIPM Decision CIPM/108-38 of October 2019 the Practical Arrangement between the BIPM and the Preparatory Commission of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) on collaboration on the metrological traceability of measurements of infrasound, seismic activity and radioactivity was signed by Dr Lassina Zerbo, Executive Secretary of the CTBTO, on 4 May 2021 and by Dr Martin Milton, Director of the BIPM, on 10 June 2021.

The BIPM assists the CTBTO in its role to provide its States Signatories with data and products of the highest quality standard including reaching compatibility and adherence to the International System of Units (Système International d'Unités, the SI), metrological traceability and measurement uncertainty. The CTBTO assists the BIPM in its role of coordinating the development and validation of Calibration and Measurement Capabilities (CMCs) for measurements in the field of low-frequency sound and vibration as well as radionuclide particulates and gases.

Pursuant to this Practical Arrangement representatives of the BIPM will be invited to attend meetings of the CTBTO related to metrological traceability and measurement uncertainty, including the coordination of Pilot Studies and the development and validation of CMCs. Likewise representatives of the CTBTO will be invited to attend the meetings of the Consultative Committee for Acoustics, Ultrasound and Vibration (CCAUV) and the Consultative Committee for Ionizing Radiation (CCRI).