People who deal with chemicals should know what dangers they face and how to protect themselves from them. Therefore, warnings have been provided by standard institutions for how to work with these materials, how to store and transport them, the dangers and adverse effects of these materials. Factories producing chemicals are required to include standard signs to provide safety information and chemical hazard signs on the packaging of chemical substances.
These warning signs are well-known symbols that are defined and provided by the World Standard Organization to notify people.

When dealing with chemicals, R and S phrases are used:
Warning S (the first letter of the word Safety):

Each label must contain safety  S phrase that describe how to work safely with the substance for the user.

Warning R (the first letter of the word Risk):

Each label must contain safety R phrase that indicate the possible risks of working with the substance for the user.
The following is the table of R and S phrases.

Also, the hazard pictograms that form part of the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) are one of the key elements for labeling containers that indicate chemical, flammable, and environmentally harmful warnings.

Examples of these pictograms: