Well, there are a few different things you can do. If there is a Shop Steward or Health and Safety Rep who works on your site, you should let them know first. If not, then there are still lots of ways you can work this out. If you're a union member and there's nobody in your workplace that you feel comfortable reporting it to, you can submit an alert form <here> to our OHS department who will endeavour to get in touch with you and help you with the issue.
If you believe you are in an extremely dangerous environment that demands urgent attention call the union office immediately on 08 9228 6900 or email firstname.lastname@example.org