Risk and Safety Statements

Risk and Safety Statements, also known as R/S statements, R/S numbers, R/S phrases, and R/S sentences, is a system of hazard codes and phrases for labeling dangerous chemicals and compounds. The R/S statement of a compound consists of a risk part (R) and a safety part (S), each followed by a combination of numbers. Each number corresponds to a phrase. The phrase corresponding to the letter/number combination has the same meaning in different languages—see 'languages' in the menu on the left.

In 2015, the risk and safety statements will be replaced by hazard statements and precautionary statements in the course of harmonising classification, labelling and packaging of chemicals by introduction of the UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS).

The R/S statement code for fuming hydrochloric acid (37%):

The corresponding English language phrases:

Dashes separate the phrase numbers. They are not to be confused with range indicators.

Slashes indicate fixed combinations of single phrases.

More detailed hazard and safety information can be found in the material safety data sheets (MSDS) of a compound.

...
Wikipedia