Surprising about linseed oil! I wonder how many oil soaked rags he had accumulated in the trash can. It looks like he was using blue paper shop towels.
I have a welding/grinding area in one corner of my shop adjacent to an overhead door. When I set this up years ago I installed cement backer board on the 2x4 framing in the welding corner, as a wall covering. I figured cement doesn't burn very well, so it might be good fire suppression material to withstand sparks from acetylene tour resulting from my cutting, grinding operations and the occasional welding job. There is NO flamable material within the 15' spark radius of the grinding corner. Also use a surplus mine ventilation fan to exhaust fumes and live sparks out the open shop door. Any rags used with solvent get hung out to dry, either outside, or over the edge of the a trash can, before disposal.
Basic precautionary stuff. But never hurts to talk about it to help prevent something from going wrong in the future.
Glenn