The nine hazard pictograms, one at a time

Most of us learn the red diamonds the way we learn road signs: we see them so often that they stop registering. That is a pity, because each one is a small and precise message. The diamond on the back of a drain cleaner is not decoration, and it is not the same diamond as the one on a can of spray paint. Once you know the nine shapes, you can stand in front of a cupboard and sort the bottles by what they can actually do.

Here are all nine. The five you are likely to meet at home come first, the four rarer ones are kept short, and a garage shelf is read at the end.

Where the diamonds come from

The pictograms belong to the Globally Harmonized System of Classification and Labelling of Chemicals, usually shortened to GHS. It is a United Nations system, available since 2003, and its whole point is that the same hazard should look the same on a label wherever the product was made. The GHS is not a law in itself. Countries and regions bring it in through their own rules.

In the European Union that rule is the CLP Regulation, Regulation (EC) No 1272/2008 on the classification, labelling and packaging of substances and mixtures. It entered into force on 20 January 2009 and gradually replaced the older EU system. The two directives behind the old system were repealed on 1 June 2015. Great Britain uses the same pictograms under its own copy of the regulation, known as GB CLP. In the United States, OSHA's Hazard Communication Standard uses the same symbols for chemicals in the workplace. US household products are labelled under different laws, which is why a bottle from an American supermarket may carry no diamonds at all.

The design rules are the same wherever the system is used. The pictogram is a square set on its point, with a black symbol on a white background and a red border wide enough to see clearly. OSHA's standard even spells out that an empty red diamond is not a pictogram and is not allowed on a label. Each pictogram also appears only once on a label, even when two different hazards call for it. The UK Health and Safety Executive has a plain page showing all nine GB CLP pictograms if you want the images in front of you while you read.

The five you will meet under the sink

Corrosion (GHS05)

Two test tubes pour liquid, one onto a hand and one onto a bar of metal, and both are being eaten away. This pictogram covers products that can burn skin, products that can cause serious eye damage and products that are corrosive to metals. At home it turns up on oven cleaners, strong drain cleaners and some descalers. The hazard statement beside it often reads "Causes severe skin burns and eye damage".

My habit with this one is simple: the bottle goes on the highest shelf, and the gloves and eye protection the label asks for come out before the cap does.

Exclamation mark (GHS07)

A black exclamation mark. It is the broadest of the nine and the one you will see most often. OSHA's summary lists skin and eye irritation, skin sensitization (allergic skin reactions), acute toxicity at the "harmful" level, narcotic effects such as drowsiness, and irritation of the airways. Under the European rules it can also mark a product as hazardous to the ozone layer. Laundry detergents, many surface sprays and plenty of dishwasher products carry it.

Read it as "less severe than the other pictograms that could have been used", rather than "mild". The rules make the exclamation mark step aside when a stronger pictogram already covers the ground. Under CLP, if the skull and crossbones applies, the exclamation mark does not appear at all. If the corrosion pictogram applies, the exclamation mark does not appear for skin or eye irritation. So a drain cleaner with corrosion and no exclamation mark has lost nothing.

Flame (GHS02)

A flame standing on a line. It means flammable: liquids, gases, aerosols and solids that catch fire easily, along with some substances that heat up by themselves or give off flammable gas when they meet water. You will find it on aerosol cans, methylated spirits, lighter fluid, paint thinners, some polishes and alcohol hand gels. Typical hazard statements are "Extremely flammable aerosol" or "Highly flammable liquid and vapour". The storage message is the same every time: away from the boiler, the cooker, heaters and direct sun.

Health hazard (GHS08)

The outline of a person with a starburst across the chest. This is the pictogram people misread most, because it looks the gentlest of the lot and it is not. It covers serious or longer-term effects: substances that may cause cancer, damage genetic material or harm fertility, substances that can trigger asthma-like reactions when breathed in, damage to particular organs, and aspiration hazard.

Aspiration is the one that matters most in a family home. Some thin oily liquids, lamp oils and some solvent-based products among them, can get into the lungs if they are swallowed. The hazard statement for that reads "May be fatal if swallowed and enters airways". The pictogram alone cannot tell you which of these effects applies, so this is the diamond where the words beside it matter most.

Environment (GHS09)

A dead tree and a dead fish on a riverbank. It means toxic to aquatic life, in the short or long term, and the usual statement is something like "Toxic to aquatic life with long lasting effects". It appears on some insecticides, weedkillers, wood treatments and a few cleaning products. OSHA treats this pictogram as non-mandatory on US workplace labels, which is why some American charts show only eight. Under CLP it is required where it applies. For a householder it is mostly a disposal message: whatever is left over goes to a household hazardous waste collection, never down the sink or an outside drain.

The four you are less likely to meet

Skull and crossbones (GHS06)

Acute toxicity at the "toxic" or "fatal" level, meaning a small amount swallowed, breathed in or taken in through the skin can do serious harm. Few everyday cleaners carry it, but you may find it on some pest-control products and on older garage stock. If something with this symbol is in the house, it belongs in a locked cupboard or box, not just a high one. The safety shelf has the kinds of lockable storage worth looking at.

Flame over circle (GHS03)

A flame above a ring. It marks oxidizers: substances that release oxygen and can make a fire burn much more fiercely, or help start one when they meet combustible material. Some pool chemicals carry it. Keep them dry, in their original containers, and well apart from fuels, garden products and other chemicals.

Gas cylinder (GHS04)

A gas bottle lying on its side. It means gas under pressure: the container may burst if it is heated, and some very cold gases can cause cold burns. You are most likely to see it on cylinders for barbecues, camping stoves or welding. Under the CLP rules on which pictogram takes precedence, the gas cylinder becomes optional when the flame or the skull and crossbones already applies, which is why many flammable gas canisters show only the flame.

Exploding bomb (GHS01)

A bomb bursting apart. It covers explosives and some unstable substances that can react violently on their own. It is rare in an ordinary home. If you ever find it on an unmarked or unfamiliar tin in a shed, leave the tin closed and ask your local council's household hazardous waste service how it should be collected.

The older orange squares

Before CLP, European labels used a different set: black symbols on orange squares, each with a letter code and a word underneath. The old risk phrases have since become hazard statements, and the safety phrases have become precautionary statements. Many sheds and garages still hold tins from that time, so it helps to recognize the old codes.

Treat the right-hand column as a rough guide, not a legal conversion. The two systems classify products differently, so an old "Harmful" tin might carry the exclamation mark under today's rules or the health hazard diamond, depending on why it was harmful. The more useful lesson is the age. A tin still wearing an orange square has been on that shelf for a long time. Lids rust, contents separate and labels fade, so these are often the first candidates for a trip to the drop-off.

A worked example: one garage shelf

Here is the kind of shelf many of us have. The products are made up but typical, and I read them left to right, pictograms first.

1. A tin of solvent-based wood stain with the flame and the health hazard. The flame tells me where it can live (not next to the boiler, not in the hot car). The health hazard sends me to the words, and the words say "May be fatal if swallowed and enters airways". That moves it to the top shelf, firmly closed.
2. A patio cleaner with the corrosion pictogram. Top shelf, gloves and eye protection when used, as the label asks, and never decanted into anything else.
3. A weedkiller concentrate with the exclamation mark and the environment pictogram. Storage is high and closed. The environment diamond is a note to myself about what happens to the last inch in the bottle: it goes to a hazardous waste collection, not down the drain.
4. An aerosol of de-icer with the flame. Not left in the car on a sunny day, kept away from heat, and stored upright.
5. An old tin with an orange Xn square. I check the lid and the container. If either has seen better days, or if I cannot remember what it was for, it goes in the box for the next drop-off.

Sorted like that, the shelf has a logic: anything that can burn skin or cause harm if swallowed sits highest, flammables sit away from heat, and anything marked for the environment has a planned exit.

What the pictogram does not tell you

A pictogram names the type of hazard. It does not tell you how serious it is or what to do about it. For that, read the rest of the label: the signal word, which is either Danger or Warning; the hazard statements, which say exactly what the product can do; and the precautionary statements, which tell you how to use, store and dispose of it. Our Reading Labels section goes through those parts one at a time.

A missing pictogram is not a safety rating either. Some products fall below the thresholds for classification and still deserve care, and some product types, such as medicines, are labelled under different rules altogether. Every bottle under the sink belongs out of reach of children, diamond or no diamond.

If something has gone wrong

If someone may have swallowed a product, breathed in its fumes or splashed it on their skin or in their eyes, call your local emergency number or a poison center now, and keep the product or its label in your hand while you talk. In the US, Poison Help is 1-800-222-1222. In the UK, call NHS 111, or 999 in an emergency. Across the EU, the emergency number is 112. If the person is unconscious, having trouble breathing or having a seizure, call 911, 999 or 112 straight away. Our official help page lists where to find other contacts.

The label is what the person on the phone will ask about, and the pictograms are often the quickest part of it to describe. Knowing that the diamond on the bottle is "the one with the test tubes" is a small thing to learn, and it pays off on the one day you need it.