According to current legislation, chemicals and mixtures of chemicals have to be labelled according to the safety/hazard of the material. Current legislation, which went into force December 1, 2010, is named GHS (Global Harmonised System), and regarding labelling of chemicals it consists of what is called H/P phrases (Health & precaution phrases) and a hazard symbol with a signal word.
Before this we had a system called "Risk and safety phrases", or R/S phrases, and hazard symbols with test. These were only for European labelling. This labelling is currently being settled, as the last of the pure chemicals had to be relabelled December 1, 2012, and for mixtures the last ones have to be relabelled June 1, 2017. Most likely you will find both chemicals and material safety data sheets with the old labelling for many years after this.
For all intents and purposes H/P phrases is doing the same as R/S phrases: Information for the user about risks pertaining the use of the chemical and the required safety precautions. The wording of the individual H/P phrases are different from the R/S phrases, reflecting today's international society, greater knowledge about chemicals, and increased focus on safety.
An example on the difference between the two labellings can be seen here:
Hydrochloric acid (20-25 %)
|Risk and safety phrases||GHS Hazard and Precautionary Statements|
|R36/37/38 Irritating to eyes, respiratory system and skin.
S2 Keep out of the reach of children.
S26 In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.
S24/25 Avoid contact with skin and eyes.
Causes serious eye irritation. (H319)
May cause respiratory irritation. (H335)
Causes skin irritation. (H315)
Wear protective gloves/protective clothing/eye protection/face protection. (P280)
IF ON SKIN: Wash with plenty of soap and water. (P302/352)
IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. (P305/351/338)
Avoid breathing dust/fume/gas/mist/vapours/spray. (P261)
IF INHALED: Remove to fresh air and keep at rest in a position comfortable for breathing. (P304/340)
If eye irritation persists: Get medical advice/attention. (P337/313)
Symbol: Exclamation mark
Signal word: Warning
The list with R/S phrases can be seen here: R/S phrases
The list with H/P phrases can be seen here: H/P phrases
The list with the discontinued European pictograms for labelling and classification of chemicals can be seen here: European hazard symbols and classes (defunct)
List of current pictograms for labelling of chemicals can be seen here: GHS labelling and classification of chemicals
At transportation of chemicals, the chemicals have to have a separate type of labelling called transport classification. This is for both transport collies, tanks, containers, cars and whatever else you might use for transport. Chemicals, in this case, is also consumer goods that one normally wouldn't consider chemicals, e.g. fireworks and detergent.
Hazard classes and the pictograms going with them can be seen here: ADR transport pictograms and hazard classes