These Hazard Communication Standard pictograms cut through language barriers and let everyone on the jobsite know what kind of threats a substance poses.

There are many different operations happening at once on a construction site. Some may involve the use of hazardous materials. No matter what trades workers are engaged in, everyone needs to be aware that there are potentially dangerous substances in use.

Through its Hazard Communication Standard (HCS), OSHA requires the manufacturers or distributors of hazardous chemicals to label them with a pictogram (on the tank or drum, for instance) that alerts workers to the type of hazard posed. OSHA enforces the use of eight pictograms, with a ninth being optional.

In addition to the pictogram, labels for hazardous chemicals must contain the word “danger” or “warning” (“danger” indicates a more severe threat), a hazard statement that describes the hazard (for example, “Causes damage to kidneys through prolonged or repeated exposure when absorbed through the skin”) and a precautionary statement that describes precautions that should be taken.

Here are the nine pictograms and what they mean.

Skull and crossbones

When a single exposure to a substance, or multiple exposures with 24 hours, can potentially make someone sick or even cause death, that substance gets this label. Acutely toxic chemicals on a construction site can include the solvents in paint thinners and degreasers. Mercury and lead are examples of substances that are chronic toxins vs. acute toxins.

Flame over circle

This pictogram indicates an oxidizing material — one that provides the oxygen other materials need to burn. If an oxidizing material gets too close to substances like some peroxides or nitrates, it could cause those substances to burst into flame or explode without an ignition source, like a spark or flame.

Flame

The flame pictogram is used for flammable materials, including those that emit flammable gas and those that can ignite spontaneously. On a construction site, these could include fuel for vehicles and equipment.

Exploding bomb

Explosives, such as dynamite, get this pictogram. Some peroxide-containing solvents can also explode if handled or stored incorrectly.

Corrosion

Corrosive materials can cause damage the skin and eyes and anything else they come in contact with, sometimes including metal. Battery acid is a corrosive agent that someone working on vehicles might come in contact with, and construction crews could be exposed to corrosive chemicals like sulfuric or hydrochloric acid while working in chemical plants or other manufacturing operations that use these substances.

Gas cylinder

This pictogram indicates gas under pressure. Gases under pressure are gases stored in a container at 29 psi or more and that are liquefied or liquefied and refrigerated. Gases like acetylene (used in welding) can explode if heated.

Exclamation mark

This is usually used to indicate an irritant (either skin or lung) or skin sensitizer. Exposure to skin irritants like solvents, thinners and adhesives can lead to contact dermatitis, a skin condition characterized by redness, swelling and pain. Some mild corrosives are also irritants.

Health hazard

These chemicals may cause chronic and even fatal illnesses like cancer or respiratory disease, as well as birth defects. Examples include benzidine (found in some paint dyes) and ethyleneimine (found in adhesives and binder).

Environment

This is the optional pictogram. It calls out chemicals that are toxic to the aquatic environment. These chemicals can run off into water systems, including rivers, lakes, ocean, streams and aquifers, killing or contaminating aquatic life and making sources of drinking water toxic.

Contractors’ responsibilities

When contractors introduce hazardous chemicals to a jobsite, they are required to provide safety data sheets (SDS) for each substance and ensure that the substance is properly labeled. In addition, employers are responsible for ensuring that their employees wear the appropriate PPE for working with chemicals.

For more information on chemical safety, visit the OSHA’s Chemical Hazards and Toxic Substances website.