Can the Commissioning (Initial) Assessment of my Local Exhaust Ventilation (LEV) be done at the same

It is preferable to have the Commissioning (Initial) Assessment completed once the extraction system has settled into normal operation conditions.

The HSE guide to The Maintenance, Examination and Testing of Local Exhaust Ventilation [dust & fume extraction systems] states that the Commissioning or Initial Appraisal will be carried out soon after installation.

It may be necessary to allow the plant to settle into normal operating conditions for a short period before the initial appraisal is carried out to ensure that the results obtained are valid to issue as a basis for long term comparisons.