In June of 2011, the fourth revised edition of the UN’s Globally Harmonized System of Classification and Labelling of Chemicals (GHS, Rev.4) was issued.
The changes in the latest revision include two new hazard categories : chemically unstable gases and non-flammable aerosols. These new categories account for hazards not previously addressed where special precautions are needed when handling, storing or transporting these items. Acetylene, a commonly used welding gas is an example of a ‘chemically unstable gas’. Acetylene is unstable and can explode without an ignition source at pressures as low as 25 psi (172 kPa). For that reason, Acetylene is normally sold ‘dissolved’ in porous Acetone to allow for higher pressures. Additionally, a non-flammable aerosol, still presents a pressurization hazard and can explode if heated, even though it is not technically ‘flammable’.
The 4th Revised Purple Book provides additional clarification of some of the hazard criteria, such as for gases under pressure or mixture cutoffs for Category 1 Carcinogens; and further rationalization of precautionary statements, such as ‘P251 – Do not pierce or burn, even after use’ for non-flammable aerosols as well as flammable aerosols.
Also added, is a new special labelling arrangement for materials that are only corrosive to metals and not corrosive to the skin and eyes. The new option for the Competent Authority is to allow the hazard pictogram for the ‘Corrosive to metals’ category to Continue Reading…