Its interesting how research into the use of propylene glycol as an air sanitizer was very widespread in the 1930s and 40s, and then somehow just stopped after that.
Agreed. I was rather taken aback that research seemingly “just stopped” and I couldn’t make any further citation of continuing research. The vaping companies make citation of the noted paper in defense of their products, but no public health application beyond the laboratory has ever been utilized (from what I was able to ascertain).