If the company in question is OHSAS 18001 certified by a reputable accreditation body, such as UKAS (others are available), then they are required to continually audit, internally and externally, against the standards in order to maintain their accreditation. IMO, CHAS is easily achieved by almost any company who wants it, especially if guided by someone who knows how to tick the boxes for them! Again IMO, OHSAS 18001 is not easily achieved and goes into much more detail, looking at processes of how H&S is managed. OHSAS 18001 is not easy to achieve without the buy-in of a company.

This is just my opinion, others may well not agree.

Personally, I think 18001 is more than equivalent to CHAS (with respect to stage 1 assessmnet of company competency).

However, the real issue is which part of the core competence criteria do you think 18001 fails to demonstrate? Remember that the legal requirement is not to demonstrate that they have anything equivalent to CHAS, it's to demonstration that they meet an adequate competency requirement. I believe 18001 does this (easily).

Management systems take considerable effort to achieve unlike CHAS. They also signify a structured approach to many areas including training and competency. You will also find records of audit to demonstrate their ongoing activity.

I would also like to see a separate competence management process for absolute completeness. In fact this latter is probably more important than any other management system/process

Competent people managed by competent persons undertaking work as set out by a competent board

Bob