Please help me to understand PSR law

Please help me to understand PSR law

We are a QS firm who also works with value assessment of projects. We usually work with construction firms who are into building residential properties. But, this time we are working with a small business who are into small-scale steel production. They provide raw material to garages and auto modification businesses. Since the client is based in Ontario, we have to deal with a new rule called PSR (pre-start health and safety review) that is mandated by the Ministry of Labour. As per the law, every business has to get a review done by any professional engineering consulting firms in Ontario(https://www.hite-engineering.com/). That means that we have to include the cost of review and also the cost of safety measurements in our assessment. I checked the website of the Ministry of labour, and it states that A PSR would be required when a factory produces aluminum or steel or is a foundry that melts material or handles molten material. At the same time, the exemption rule states that PSR is not required if the protective element was installed at the time the apparatus was manufactured. That statement made me confused. What do they mean by such a statement here? And, does PSR apply to every business that falls under a category irrespective of the size of the business? I hope someone here will help me out.
Thank you.