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Categorizing health hazards

Although the NFPA can provide specific information on handling dangerous substances, it requires a little training to interpret, and isn’t meant for communicating the essence of a hazard. For communicating more generally about chemical hazards, OSHA developed its HCS (or Hazard Communication System) in 1983. As part of its efforts to categorize dangers, OSHA breaks down hazardous chemicals into nine categories, each comprising several general categories of danger. The HCS is currently in flux due to new international agreements inaugurating the Globally Harmonized System of Classification and Labeling of Chemicals (or GHS for short), but for the time being (as of 2012), the HCS’s pictograms are considered compliant for non-transport purposes.

These pictograms are necessary but not sufficient for labeling for transport – to comply with GHS, a label needs not only a pictogram, but also a signal word indicating the extent of the chemical’s danger. It also requires other information on handling and ownership of the compound.

Health Hazard Pictogram
The Health Hazard pictogram can warn of reproductive toxicity, target organ toxicity, aspiration toxicity, a respiratory sensitizer, a carcinogen or a mutagen.
Flame Pictogram
The Flame pictogram can mean flammables, pyrophorics, self-heating, self-reactive substances, organic peroxides, or anything that emits flammable gas.
Poison Symbol
The international symbol for poison, the skull-and-crossbones means acute toxicity.


Corrosion Symbol
The Corrosion symbol doesn’t just mean acidity – it can also warn of substances that may corrode metals that they touch, eye damage or skin burns.
OSHA’s Explosion Symbol
Another fairly obvious pictogram, OSHA’s Explosion symbol can mean explosives, but it can also alert workers to self-reactive substances or organic peroxides
Gas Cylinder Symbol
The Gas Cylinder means pretty much what it says – compressed gas.
Oxidizing Chemicals Symbols
The Flame Over Circle symbol specifically means oxidizing chemicals, like perchlorates and nitrates.
Danger Symbols
The Exclamation Mark is a catch-all for dangers ranging from skin and eye irritants, skin sensitizers, acute toxicity, narcotic effects, respiratory tract irritants and substances that are dangerous to the ozone layer.
Aquatic Toxicity Symbols
The lonely non-mandated chemical warning among OSHA’s nine, the Environment warning (which typically indicates aquatic toxicity).
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