Originally Posted by Paul the Tool

Yes, you should *always* read, & carefully follow, any safety instructions on these kind of products.
I doubt you'd have to go as far as leaving your home for the night though! Since we're talking about a conservatory it should be pretty easy to isolate it from the rest of the house (keep the connecting door closed) & ventilate the area well. With a painted on treatment, which is what I was thinking of, that should be sufficient safety measures in most cases, as it's most likely to be the treatment's solvents that you're gonna have to worry about breathing (still potentially nasty, but not as bad as solvent+fungicide).
Obviously if you're using some kind of spray on treatment then you probably want to at least be wearing a dust mask or similar. Once again the product container should tell you if this (or any other) saftey precautions are needed.