a. Class IIIA (beam irradiance 2.5 mW/cm²), Class IIIB and Class IV lasers: Require the ANSI DANGER sign format: white back-ground, red laser symbol with black outline and black lettering (see Appendix III:6-4). Note that under ANSI Z 136.1 criteria, area posting is required only for Class IIIB and Class IV lasers.

b. Class II or Class IIIA areas (if area warning is deemed unnecessary by the LSO): All signs (and labels) associated with these lasers (when beam irradiance for Class IIIA does not exceed 2.5 mW/cm2) use the ANSI CAUTION format: yellow background, black symbol and letters.

c. During times of service and other times when a temporary laser-controlled area is established, an ANSI NOTICE sign format is required: white background, red laser symbol with blue field and black lettering. This sign is posted only during the time when service is in progress. Examples of area warning signs and logotype designs are given in Appendix III:6-4.