That you just need to talk to them about.
As for how to do a risk assessment you need to start by identifying the risks for the activity you are undertaking, classifying how severe and likely the risk is to occur.
Then look at what measures could be implemented to control it, then how that affects the risk and likelihood after the control measures.
For example heating PVC will create fumes, quick research shows they are a carcinogen.
So before control measures the risk is HIGH, the likelihood is HIGH, overall risk is VERY HIGH.
Proper extraction could reduce that risk to HIGH, the likelihood to LOW, the overall risk as LOW/MEDIUM.
Something like that…
Best to start by asking the directors though.