> hydrogen fire has no color and is only noticeable when something else starts to burn I used to work at a company that had a hydrogen workshop. There were UV

> hydrogen fire has no color and is only noticeable when something else starts to burn I used to work at a company that had a hydrogen workshop. There were UV detectors all over the place to detect hydrogen flames. It was always fun berating the occasional poor sap who fired up the arc welder without making the area hydrogen-safe and pausing the detectors in the area. This inevitably resulted in evacuation of the building and the arrival of a special firefighting unit equipped to deal with hydrogen fires, all at great cost to the company.