A Guide to Chemical Hazard Symbols

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Back to some chemistry basics for today’s post, with a look at the nine different hazard symbols commonly used to warn of chemical dangers. These symbols are frequently encountered in the lab – and also on some household products – and whilst some are self-explanatory, others can require a little more in the way of explanation, which is what this graphic aims to do.

Initially, it should be noted that these hazard symbols are primarily used in the EU. The manner in which hazardous chemicals are labelled elsewhere has previously differed. For example, in the US, the ‘fire diamond’ system is often used, whilst in Canada, similar-looking symbols to the EU (but with some variances) can be utilised. The new label system  is referred to as the Global Harmonised System of Classification and Labelling of Chemicals – a bit of a mouthful, which is often shortened to GHS, and which aims to standardised the symbols used worldwide to avoid regional differences.

The EU’s symbols haven’t even always looked like those featured in the graphic – this particular set have only been in use since 2010. Previously, they looked fairly similar, but were set on orange squares, instead of the diamonds now employed. There’ve also been a few changes and additions to the symbol set.

The most noticeable of these is the disappearance of the ‘irritant/harmful’ symbol, which was previously a black x on an orange background. This symbol has now been consigned to chemical history; hazards that were previously categorised under it are now found under a variety of the other symbols, depending on the particular chemical. The closest thing to a replacement is the exclamation mark symbol, which denotes a moderate hazard.

The toxic symbol’s definition has also changed slightly. Previously, it would have denoted any toxic hazard, whereas, with the introduction of the health hazard symbol, it now refers strictly to substances with acute toxicity. This means anything that can cause toxic effects after limited exposure, single dose, or multiple doses within a small space of time. Substances with longer term health effects as a consequence of exposure now fall into the ‘health hazard’ category.

Obviously, if you don’t work in a chemistry laboratory, you might wonder what the use is in being able to discern what these hazard symbols mean. A quick look in your kitchen cupboard should, however, reveal one or two. Oven cleaners and toilet cleaners in particular often contain chemicals in concentrations that require one of these hazard symbols to be used, and whilst it’ll also feature a description of the particular hazard, it’s still useful to know what they mean. The deadline for switching over to the new labelling system is this June, so currently you may have some products with the old labelling system, but soon they’ll all follow the new one identified here.

As an important final note, the icons shown in the graphic, whilst designed to be as close to the GHS symbols as possible, are not the official symbols. If you have any responsibility for hazardous chemical labelling, these symbols should not be used – the official labels, which can be found via the second link in the references below, should be used instead.

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References & Further Reading