I am Sure when my son was a steward their they were told it is a fire hazard.
Probably was told that. Unfortunately the person that told him obviously had no knowledge.
I am a sparks, have installed fire alarm systems, and have spent the last two years on working on one of the most sophisticated systems out there. The system is used on government buildings, submarines etc. Having inquired and vaped next to smoke detectors and the Vesda system which sniffs the air and is a far far more sensitive system than the smoke detectors, i can assure you that your son was fed a load of smoke and mirrors.