HMIS stands for Hazardous Materials Identification System, an in-house labeling system copyrighted by the American Coatings Association (ACA). It was originally developed for use by the paint manufacturing industry to indicate chemical hazards in the workplace. The system has since spread to other service and manufacturing industries. HMIS® labels appear as a rectangle-shaped block of colored bars with hazard ratings of zero through four, plus personal protective equipment symbols/letters and a carcinogen indicator.
Under the revised (May 2024) HazCom Standard, OSHA has indicated that the use of the HMIS system is still permissible in house, but HMIS labels may not appear on containers leaving the workplace. See 29 CFR 1910.1200(f)(6).