Hazard Communication and Laboratory Safety standards. If chemicals are not exempted or covered under other regulations as indicated above, OSHA then says labels are required for them if they are hazardous chemicals. OSHA defines a hazardous chemical as anything that is a physical or health hazard.
Physical hazards are pretty straight forward.
They include flammable and combustible liquids, compressed gasses, explosives, organic peroxides, oxidizers, pyrophorics, and water reactives. Dram vials and other small containers can be difficult to label because of their size. In this instance, we recommend that you place these items in test tube racks, boxes or other containers, and label these items instead. Labeling a shelf or draw where these chemicals are located is also possible, however any chemicals removed that do not have a full chemical name, must remain under your direct control and supervision. Most labels will provide you with additional safety information to help you protect yourself while working with substances.