The wording on any safety sign should be concise and easy to read, according to ANSI Z535.2-2011, Section 8. The size of the lettering must be of a size that enables a person with normal vision, including corrected vision, to read the safety sign message panel text at a safe viewing distance from the hazard. The signal word letter height should be at least 50 percent greater than the height of a capital H in the message panel wording. The minimum safe viewing distance refers to the closest distance a person can be to the sign and still have time to follow the safety sign’s message to avoid the hazard.

Source: www.grainger.com