ISO 9001 only requires
7.1.5.2 Measurement traceability
When measurement traceability is a requirement, or is considered by the organization to be an
essential part of providing confidence in the validity of measurement results, measuring equipment
shall be:
a) calibrated or verified, or both, at specified intervals, or prior to use, against measurement standards
traceable to international or national measurement standards; when no such standards exist, the basis
used for calibration or verification shall be retained as documented information;
There is no requirement for an accredited lab just traceability which when it comes down to it is no big deal. This is why they always stress traceability on there documents