Safety Symbols and Their Meanings

Safety signs can be a tricky business. Some have words and a clear message, but many rely on visual symbols to warn of potential danger. This is an effective way to communicate potential hazards – as long as workers understand what the symbols mean.

There are two different types of safety symbols: one refers to general safety protocols, while the other is used specifically for labeling chemicals that may be hazardous.

Since most workplaces have a combination of both, it’s important to understand each of them.

Why Use Safety Signs and Symbols?

These pictures may not say a thousand words, but they are universally recognized symbols that transcend language. No matter where you’re working, you’ll be able to understand the potential hazards you face simply by looking at the posted symbols.

The best occupational health and safety programs use a series of signs and symbols to convey a complete message.

For example, a hazardous gas symbol may alert workers to the potential presence of a harmful gas. But an accompanying sign mandating the use of a gas mask takes it a step further by telling workers how to handle the hazard.

Signs and symbols are no substitute for training, but they do serve as important reminders. They can be particularly helpful for workers who are not familiar with a specific area or process. A simple sign with a safety symbol allows workers to efficiently identify the potential hazard and make an immediate decision.

4 Key Types of Safety Symbols

Most safety signs and symbols fall into one of four categories:

• Prohibition
• Warning
• Mandatory
• Emergency

Each category has its own specific color and sign shape that remains consistent around the world as per safety regulations.

By getting to know the key characteristics of each type of symbol, you’ll be able to easily identify whether a sign is asking you to stop doing something, start doing something, take precautions, or advising you of emergency equipment or facilities.

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Hazardous Chemicals Communication Standard and Symbols

Canada’s Workplace Hazardous Materials Information System (WHMIS) and OSHA’s Hazard Communication Standard (HCS) align with and draw on the Globally Harmonized System of Classification and Labeling of Chemicals (GHS). Using this international system helps ensure consistency in the classification of chemicals and the communication of hazard information on labels and safety data sheets.

The system uses pictograms on labels to alert users of the chemical hazards they may be exposed to. Every symbol consists of a black pictogram on a white background, framed by a red border. There are nine different pictograms, each representing a different chemical hazard classification.

Health Hazard

• Carcinogen
• Mutagenicity
• Reproductive toxicity
• Respiratory sensitizer
• Target organ toxicity
• Aspiration toxicity

Flame

• Flammables
• Pyrophorics
• Self-heating
• Emits flammable gas
• Self-reactives
• Organic peroxides

Exclamation Mark

• Irritant (skin and eye)
• Skin sensitizer
• Acute toxicity (harmful)
• Narcotic effects
• Respiratory tract irritant
• Hazardous to ozone layer

Gas Cylinder

• Gases under pressure

Corrosion

• Skin corrosion/burns
• Eye damage
• Corrosive to metals

Exploding Bomb

• Explosives
• Self-reactives
• Organic peroxides

Flame Over Circle

• Oxidizers

Environment

• Aquatic toxicity

Skull and Crossbones

• Acute toxicity (fatal or toxic)

Common Types of Safety Signs and Symbols of Note

There are numerous safety pictograms that aren’t derived from the GHS but are still highly important. 

Some of them will be familiar to most people. We all have a pretty good idea of the risks we’re facing when we see the Biohazard symbol, for instance. 

Others aren’t so obvious. The symbols provide vital information about the hazards in your work environment, but unless you know what they mean, they won’t do much to keep you safe.

So, let’s look at a selection of the signs, symbols, and pictograms you might encounter on the job and what they mean.

Be aware, however, that this is by no means a comprehensive list. This is a selection of the safety symbols for some of the major workplace hazard categories, but they might not be the only ones. 

Chemical Safety Signs and Symbols

Ionizing Radiation

This symbol signals the presence of ionizing radiation. This type of radiation is a significant hazard that has the potential to change the structure of molecules (including DNA) in such a way that it could disrupt normal cell functioning.

In the right doses, ionizing radiation can cause germ cell damage, fetal damage, radiation sickness, or cancer. 

You’re already familiar with this radiation symbol – if only because you’ve seen it so often in movies. But it’s not common in most worksites. It’s not even present everywhere there’s a radiation hazard. In some cases, like on some detectors using americium-241, you might find the generic GHS “health hazard” pictogram instead. Why? Because we tend to associate the symbol with major devastating catastrophes, which doesn’t always reflect the actual level of risk.

That being said, it still appears in some contexts, such as nondestructive testing (NDT), ammonia plants, nuclear power plants, and radiology.

Emergency Shower

This sign marks the location of the emergency shower, something workers should be aware of when handling certain hazardous materials.

These emergency showers aren’t just any spot where hazardous materials can be washed off. They are purpose-built showers that must be tested at regular intervals (depending on your jurisdiction, this can be pretty specific), must deliver a specified rate of flow for a minimum period, and must deliver tepid water instead of cold.

In many workplaces, these showers are there “just in case” and don’t see regular use. This makes this symbol particularly important since it will guide workers who likely have never had to use them. 

Biohazard

This symbol indicates the presence of biologically harmful substances, such as infection agents, live viruses, bacteria, or mold. 

The biohazard symbol is probably seen on a lot more t-shirts than worksites. But in certain applications (labs, pharmaceuticals, and medical facilities in particular), it continues to be an important health and safety warning.

The biohazard symbol is used in WHMIS but is not an official GHS pictogram. Still, it remains prevalent because it is instantly recognizable and unambiguous. 

Electrical Safety Symbols

Live Electrical Equipment

This symbol is displayed where there is powered electrical equipment that could deliver a shock. A similar symbol with a “flash” to the side indicates that the equipment also poses an arc flash risk.

This basic symbol is usually accompanied by text, but knowing its meaning is still important – especially since the text is typically relevant in only one language.

High Voltage or Shock Hazard

Sometimes considered interchangeable with the basic lighting bolt symbol, this one communicates a more specific hazard. Namely, that the equipment can electrocute you.

You’re likely to see this type of sign around transformers, power plants, power panels, and other high voltage electricity-channelling equipment.

No one should enter into areas with this symbol unless they have been authorized and trained to do so.

Connect Earth Terminal to Ground

The ground symbol is used to indicate that a piece of equipment needs to be connected to “ground” or “earth.” 

This usually involves driving a ground rod to a suitable depth where the electricity can safely be discharged, rather than introducing current into the surrounding materials, equipment, or workers.

Sensitive Electronic Device

These signs are commonly seen around electronics manufacturing facilities. They aim to protect the integrity of materials or partially assembled components.

Such signage is displayed for work on containment areas that house components like circuit boards, which can be damaged or irreparably ruined by a simple static discharge. 

The basic yellow and black warning pictogram alerts a worker that there is a condition that requires their attention. In this case: don’t touch anything unless you know what you’re doing!

Fire Safety Symbols

No Smoking

This one might seem almost too obvious to include because it is so ubiquitous. It isn’t quite as prevalent as it once was, however. That’s because it used to be posted to denote the only places where smoking wasn’t permitted. Now, it’s largely been flipped so that smoking is only permitted in specially designated areas where second-hand smoke is unlikely to reach non-smokers. 

Although smoking is generally not permitted in workplaces and public areas, you might still see this sign posted where lighting a cigarette might be especially risky (near gas pumps, for example). 

In workplace settings, cigarettes, lighters, and other smoking implements are generally considered ignition sources for potentially flammable atmospheres or materials, especially since cigarettes can smolder for a long time after they’ve been discarded.

Fire Exit / Evacuation Route

This sign points the way out of a building or facility in the event of an emergency – which is not always the same way you came in.

These signs are so commonplace that we barely notice them in most places, but they become critical when the fire alarm goes off and you have to calmly make your way to the designated exit. Elevators disable when there is a fire, so these signs also discourage people from wasting time going to them instead of heading for the stairwell. 

Emergency evacuation signs are often illuminated so they can be visible in the dark or when smoke is filling the room. 

Hot Surface

This symbol is often posted near cooktops, ovens, and other heat-generating appliances. It’s also useful on machinery casings, piping and conduits, and other surfaces that may become hot as a byproduct of their operation. 

The signage warns workers to avoid getting burned by coming into contact with the surface, but also that the surface is not a place to leave a jacket, stack of boxes, or anything that could cause a fire. 

Gas Safety Signs and Symbols

No Ignition Sources

This symbol depicting a lit match is usually posted alongside No Smoking signs (most commonly at gas stations). It indicates that any ignition source has the potential to cause a fire.

It may not be the most straightforward symbol, since it doesn’t apply only to matches, but to any source of ignition. Still, it is widely used and worth knowing.

Gas Cylinder Storage Area

These signs don’t have a standard style or dimensions. There are numerous versions of this symbol and they don’t always mean exactly the same thing. 

This symbol is generally used where compressed gas bottles (such as oxygen and acetylene) are stored, which requires several safety considerations. At the very least, you should be using a spotter when operating vehicles around an outdoor storage area where this symbol is posted. 

Respirator Required

This symbol indicates that no work can take place in the area without the use of a respirator.

You might see it, for example, on vessels that have the potential to expose workers to gases and vapors, develop an oxygen-deficient atmosphere, or house respirable particles like silica or asbestos. This is common in confined spaces, where isolation can’t be completely assured and gases could be introduced. 

Poison Safety Symbols

Chemical Weapon

This symbol is used where either the precursor chemical or the full product is made or stored.

Chances are, you’ll never actually see this one in your workplace. Not unless you work for a weapons manufacturer or on a military installation. Even then, only in certain countries – the development, manufacture, and retention of these agents is banned in over 190 states through the Chemical Weapons Convention. 

Poison

This classic skull and crossbones design denotes the presence of poison or toxic materials. 

It’s the progenitor of the modern GHS symbol for acute toxicity, but is still used on some consumer products that don’t fall under workplace chemical regulations.

Noxious / Irritant

This simple X indicates the presence of irritating materials.

This symbol is more commonly used in Europe. It is particularly useful where the irritant isn’t completely contained (in a paint booth, for example) and anyone entering the area may be exposed to it.

Other Safety Symbols

Stop / No Admittance / Authorized Personnel Only

This ISO symbol acts as a general caution not to proceed any further.

This type of sign is typically posted at the entrance to restricted areas (whether for safety or security reasons), but can also be used as a reminder for those who have clearance that they are entering an area with special safety observances (such as PPE or entrance logs).

Non-Ionizing Radiation

Non-ionizing radiation is generally considered harmless to humans, but you might still see this warning symbol around equipment that operates over communications protocols, such as transmitters, routers, and cellular antennae.

Under some circumstances, these devices can interfere with one another when using shared bands, affecting the performance of electronics. 

Laser

This placard is displayed wherever there are lasers that produce significant heat, could harm workers trying to peek inside the enclosures, or could cause harm when reflecting off other surfaces.

Lasers are used in numerous applications, from measurement, infrared sensing, guidance, cleaning, and design, all the way to industrial metal fabrication. As they are extremely focused forms of light, they can be harmful to humans, especially to the eyes. 

Which Signs and Symbols Are Appropriate for Your Workplace?

To know what symbols should be in your workplace, you’ll need to perform a comprehensive risk assessment. Assessments should be conducted for each activity and at each designated workspace to make sure you identify all potential hazards. Once you have that information, you’ll know where workers will need safety reminders.

Note, however, that you might want to make sure the signs can be moved. After a while, workers become so familiar with the safety signs that they start to just be part of the background. To avoid this “sign blindness,” safety experts recommend switching up the location of your signs every so often to keep the safety message top of mind.

Conclusion

Safety signs and symbols exist to make identifying potential hazards easier. Keep things simple by spreading signs out within an area to avoid clustering them. Too many signs crammed together overwhelms workers with information and makes it less likely that they pay careful attention.

And remember that safety signs only work if everyone understands them. Conduct regular refresher training to ensure that every worker is familiar with the symbols and their meanings.

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