One of the greatest changes to OSHA’s hazard communication standard as a result of HCS 2012—OSHA’s adoption of the Globally Harmonized System of Classification and Labeling of Chemicals (GHS)—was its standardization of chemical hazard classifications. Some of these classifications are modified from what they were in the 1994 hazard communication standard (HCS 1994), and others are brand-new.
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To help employers sort out the new classifications, OSHA and the Society for Chemical Hazard Communication have created a set of Information Sheets covering five of the categories.
Corrosive to Metal
“Corrosive to metal” is a new classification category in HCS 2012; it was not covered in HCS 1994. Substances or mixtures that are corrosive to metal cause material damage to or destruction of metals. Chemicals in this category do not necessarily overlap with the category of chemicals that are corrosive to the skin and eyes.
The hazard determination for this category is generally made by testing that complies with the UN Manual of Tests and Criteria: the chemical or mixture is tested on steel or aluminum to determine the rate at which corrosion occurs. If the corrosion rate on either steel or aluminum surfaces exceeds 6.25 mm per year at a test temperature of 55°C (131°F), the label for the substance or mixture must carry the signal word “Warning,” the hazard statement “May be corrosive to metals” and the corrosion pictogram.
Manufacturers, distributors, and end users need not perform the testing themselves; information from available scientific literature and other evidence may be used to determine whether the substance or mixture meets the requirements.
You can find the information sheet for substances that are corrosive to metal here.
Flammable Gases
HCS 1994 had one category for flammable gases; HCS 2012 has two. They are based on the flammable range in air at a temperature and pressure of 20°C (68°F) and a 101.3 kPa (14.7 psi). The flammable range in air is determined using tests or calculations performed in compliance with ISO 10156 or equivalent validated methods. Mixtures must be classified based on the mixture as a whole.
- Category 1 flammable gases, at 20°C (68°F) and a 101.3 kPa (14.7 psi):
- are ignitable when in a mixture of 13% or less by volume in air; or
- have a flammable range with air of at least 12 percentage points regardless of the lower flammable limit.
Labels for category 1 flammable gases must carry the signal word “Danger,” the hazard statement “extremely flammable gas” and the flame pictogram.
- Category 2 flammable gases are any other gases that, at 20°C (68°F) and a 101.3 kPa (14.7 psi), have a flammable range while mixed in air.
You can find the information sheet for flammable gases here.
Flammable Solids
HCS 1994 had one category for flammable solids; HCS 2012 has two. It includes:
- “Flammable solids”—solids which are readily combustible or which may cause or contribute to fire through friction
- “Readily combustible solids—powdered, granular or pasty chemicals which are dangerous if they can be easily ignited by brief contact with an ignition source, such as a burning match, and if the flame spreads rapidly.
Burning rate tests are one way to determine whether a solid is flammable. In burning rate tests, a sample is placed in a testing apparatus and ignited at one end, to determine the burn rate across the sample. The standard does not require burn rate testing; information from available scientific literature and other evidence may also be used to classify the flammability of a solid.
- Category 1 flammable solids are chemicals other than metal powders for which:
- a wetted zone does not stop the fire; and
- the burning time is less than 45 seconds, or the burning rate is greater than 2.2 millimeters/second
Metal powders are classified as category 1 flammable solids if the burning time for a sample is five minutes or less. Labels for category 1 flammable solids must carry the signal word “Danger,” the hazard statement “flammable solid” and the flame pictogram.
- Category 2 flammable solids are chemicals other than metal powders for which:
- a wetted zone stops the fire for at least 4 minutes; and
- the burning time is less than 45 seconds or the burning rate is greater than 2.2 millimeters/second
Metal powders are classified as category 2 flammable solids if the burning time for a sample is at least 5 minutes but no more than 10 minutes. Labels for category 2 flammable gases must carry the signal word “Warning,” the hazard statement “flammable solid” and the flame pictogram.
You can find the information sheet for flammable solids here.
Tomorrow, we’ll look at the classification of gases under pressure and simple asphyxiants.
How does the “warning” pictogram and “may be corrosive to metals” hazard statement make sense here?
If the corrosion rate on either steel or aluminum surfaces exceeds 6.25 mm per year at a test temperature of 55°C (131°F), the label for the substance or mixture must carry the signal word “Warning,” the hazard statement “May be corrosive to metals” and the corrosion pictogram.
This is a corrosion rate of 0.25 inches/year. Unless someone is quickly using the materials, it makes sense to me that they never be stored in a container that is likely to corrode.
Granted metals will react differently. But is it worth the risk of using the less strong pictogram and lack of metal specificity?
It’s not to me…this is one I’ll be paying attention to.