Highly flammable
Products bearing this international label have a flash point of below 70°F (21°C). The containers should be kept closed when not in use, and should not be left near sources of heat or ignition. Do not breathe the vapor or spray, and keep the product away from children.
Harmful/Irritant
This international label is used to mark products classified as either harmful or irritant; each classification has its own particular warnings. In both cases, do not breathe the vapor, and keep the product away from children. Avoid contact with skin and eyes, and wash thoroughly after use.
Health label (HL)
This American label, from the Art and Craft Materials Institute (ACMI), means that the product has been reviewed by an independent toxicologist under the auspices of the American Society for Testing and Materials. (ASTM).
CP
An American label, again from the ACMI. "CP" stands for Certified Product, in which the contents are non-toxic, even if ingested, and which meet or exceed specific quality standards.
AP
Another American label from the ACMI, "AP" means Approved Product, one in which the contents are non-toxic, even if ingested.

Interpreting labels
These are the hazard labels you are likely to see on art products. Familiarity with their meanings will enable you to evaluate standards and possible hazardous use at a glance, and to use and store materials with minimum risk.

Source: Artist's Manual: A Complete Guide to Painting and Drawing Materials and Techniques. Chronicle Books, San Francisco, 1996.