The National Marker Company sign alerts workers or employees to wear a mask in a specific area where there are respiratory irritants in the air. It is mostly used to mark areas at construction sites and industrial facilities where air quality is unsafe. The legend âCAUTION â Wear mask â respiratory irritants in this area.â is printed in legible font to ensure better readability. Also, the sign features a graphic of a head wearing a full face respirator to make the message easily understandable. The sign is UV resistant, chemical resistant and graffiti proof. It has black text on yellow base and white text on black base. The rectangular caution sign complies with ANSI standards and has an NMC Sign Muscle coating to protect the text against fading, scratches, scuffing, mold, and moisture.