causing irritation of living tissue; -- used of physical stimuli.

causing pain or physical discomfort; as, an irritating burr under his stocking.

(used of physical stimuli) serving to stimulate or excite; "an irritative agent"

causing annoyance.

A irritating material, as defined by DOT, is a liquid or solid substance which upon contact with fire or when exposed to air gives off dangerous or intensely irritating fumes (not including poisonous materials: see Poison, Class A and Poison, Class B)