Cry from the heart! Please read this carefully and don't reproduce my faults! When I, Mutabor, was working in the lab, one day I felf a strong smell of burning insulation. All equipment was switched off at that moment, as well as the lighting and all electric boards. I had decided that the smell is coming from a ventilation system and decided to clear up its origin. I had went up to the techincal floor at the attic and entered the big horizontal ventilation pipe collecting exhausts from all ventilation of the block. But inside that pipe there were no smell of burning! I had crawled until the end of the pipe, but had not located a source of the smell. So I turned back and run against... the cloud of dust I had risen on the way forth! The dust was so fine, so acrid, making breath almost impossible. And there was some meters of the steel pipe ahead... I crawled and tried to avoid breathing and was thinking about inglorious end in such a place! Finally I had successfully escaped this place, but I went out almost dead!
If I had been a bit smarter, I would take a respirator with me. So I recommend to take a respirator preparing for the trip, especially if there would be a chance to crawl on belly in places like ventilation pipes, low basements and so on.