Yes, I realize using old oil directly from your tractor vs. recycled oil is very different. From lubrication point of view once used oil is still very good but impurities are not helpful and can indeed cause health issues.
One should however remember that oil recycling plants are not generally getting rid of old oil (dumping etc. it). They are making new products from it. And there is huge quantity of used oil to be recycled every year. So, even without realizing it one might be using "used" oil in various less than critical applications such as a bar oil. Not just in Finland but in other countries too. Read the small print on the bottle. And if the can is not transparent, look into the container for stuff that has settled to the bottom of it. Not all recycling or filtering processes are equal.
Concrete floor and nothing flammable around it, so just turn on the fans, cut the fuel supply way down, and let things air out. This definitely isn't a "set it and forget it" setup. Once I know the fuel is stable, I can walk away from it, go in the house and eat lunch while keeping an eye on my camera. Once warmed up and with a good fuel source, it'll burn for hours without constant fiddling.
