This Wolf No.702 flame safety lamp use only for gas testing and was originally based on design by Friedrich Pieler in 1883. Before making a test, the flame was adjusted in pure air so that the point of the flame was exactly even with the top of the hood which surrounds the burner. It ran on alcohol rather than lamp oil. It was sensitive enough that any more than minimal gas showed strongly (above 1.25%) and any reading below that minimum was deemed as potentially dangerous.
