Wondered whether to start a new thread as slightly off topic, but will try here first:

Regarding Exhaust Extraction, just wondering if, in the case of premises where garage doors are open at all times, is an Exhaust Extractor going to be of much use? (Ian thinks not).

I am wondering if workshop fumes are more the potential problem rather than the Waste Oil Heater which may be faulty (re. other thread).

At this point in time, I am so confused as to where the health problem lies - general fumes in the workshop, but doors open at all times, or Waste Oil burner (which we will check out for fault/leak).

No easy answer to the question but am so spooked by Ian's x-ray result - which as a non-smoker, can surely only have come from the workshop.