Lesson focus: hazard pictogramA red-bordered warning symbol on a label that shows what kind of danger a chemical has. warn what a substance can do; a laboratory method determines how exposureComing into contact with a hazard, for example by touching it, breathing it in or swallowing it. is prevented.
Recognise common laboratory hazard pictograms and link each hazardSomething that could cause harm, such as a hot tripod or a chemical that burns skin. to a specific risk-reduction step.
Build on earlier learning
Bunsen burnersRevisit how a specific heating hazard is linked to a practical control measure.
You will be successful when you can…
- Recognise the nine common GHS/CLP laboratory pictograms.
- Distinguish a substance hazard from the risk in a particular method.
- Link a pictogram to possible harm and routes of exposure.
- Choose a specific control measure that removes, isolates or reduces exposure.
Words that carry the science
- hazard pictogram
- A standard symbol communicating a type of chemical hazard.
- hazard
- An intrinsic property or situation with the potential to cause harm.
- exposure
- Contact with a hazard by routes such as skin, eyes, breathing or swallowing.
- risk
- A judgement combining the likelihood and severity of harm under stated conditions.
- control measure
- A specific action that reduces the likelihood or severity of harm.
- safety data sheet
- Detailed information about hazards, handling, storage, first aid and disposal for a substance.
Read the symbol, identify the risk, choose the control measure
01A pictogram describes hazard, not the whole risk
A hazard pictogramA red-bordered warning symbol on a label that shows what kind of danger a chemical has. communicates a type of harm a substance can cause. riskHow likely it is that a hazard will cause harm, and how bad that harm could be. depends on the quantity, concentration, route of exposureComing into contact with a hazard, for example by touching it, breathing it in or swallowing it., likelihood and severity within the actual method.
The same bottle may carry several pictograms. Read the complete label and follow the approved procedure; never identify an unknown substance by symbol or appearance alone.
The same chemical can carry different symbols in different bottles. A concentratedHaving a lot of a substance dissolved in a small amount of liquid, like strong squash. (strong) solution may be corrosive, while a dilute (weak) one may only be an irritant.
02Recognise what the nine pictograms communicate
The nine common categories are explosiveCan blow up suddenly, for example if it is heated, knocked or lit., flammableCatches fire easily, like petrol., oxidisingGives off oxygen, which makes other things burn more fiercely., gas under pressureGas squashed into a container, which could burst or leak if it is heated or damaged., corrosiveAble to burn or destroy skin, eyes and other materials when it touches them., acute toxicityPoisonous: can cause serious harm or death quickly, even in small amounts., irritant or harmfulCan make skin, eyes or breathing sore, or cause less serious harm., serious health hazardCan cause long-term damage to health, such as harm to the lungs, if breathed in or swallowed. and environmental hazardHarmful to plants, animals and the environment, especially living things in water..
The corrosion pictogram can warn about severe skin or eye damage and corrosion of metals. The person-with-star pictogram means serious or long-term health hazardSomething that could cause harm, such as a hot tripod or a chemical that burns skin.; aspiration hazard is only one possible classification within that broader category.
03Break the route from hazard to harm
First remove or substitute the hazard where the approved method allows. Otherwise reduce quantity or concentration, isolate the source, use suitable apparatus and ventilation, then add the specified personal protection.
A control measureSomething you do to make an activity safer, such as wearing goggles or tying back long hair. must be concrete: “keep ethanol away from the Bunsen flame and cap it after use” is useful; “be careful” is not. Stop and tell the teacher if a label is missing, a spill occurs or the planned conditions change. Put hazardous waste in the labelled waste container; do not pour it down the sink unless your teacher says so.
A pictogram warns about an intrinsic hazard. Read the label and method to decide the actual risk and control.
May explode after heat, flame, shock or friction.
Reduce the risk: Keep away from heat and impact; use only the approved small-scale method.Catches fire easily.
Reduce the risk: Keep away from flames, sparks and hot surfaces; replace lids promptly.Can cause or intensify a fire.
Reduce the risk: Keep away from fuels and other combustible material; avoid contamination.Pressurised container may burst if heated; refrigerated gas may cause cold burns.
Reduce the risk: Secure cylinders and keep them away from heat; never puncture a container.Can cause severe skin burns and eye damage, and may corrode metals.
Reduce the risk: Use eye protection and the specified small quantities; prevent contact and report splashes immediately.Small exposures may cause serious poisoning or death.
Reduce the risk: Avoid breathing, swallowing and skin contact; teacher-controlled use only.May irritate skin, eyes or airways, or be harmful at stated exposure levels.
Reduce the risk: Avoid contact and inhalation; use the labelled concentration and required protection.May cause serious or long-term effects such as organ damage, respiratory sensitisation or cancer.
Reduce the risk: Prevent exposure using the specified containment and handling procedure.Toxic to aquatic life, sometimes with long-lasting effects.
Reduce the risk: Contain spills and use the instructed waste route; never pour it away unless told to.Each control measure must interrupt a realistic route from the labelled hazard to harm.
- PictogramWhat type of hazard does the label communicate?
- ExposureHow could it reach a person or the environment in this method?
- HarmWhat injury or damage could result?
- ControlWhat specific action reduces exposure or severity?
- ReviewDo all symbols and changed conditions remain controlled?
From flammable symbol to control measure
A small bottle of ethanol has a flame pictogram and is being used while a Bunsen burner is lit.
- Identify the hazard: ethanol and its vapour are flammable.
- Identify the exposureComing into contact with a hazard, for example by touching it, breathing it in or swallowing it. condition: vapour or a spill could meet the ignition source.
- Remove the ignition source before the ethanol is opened, following the approved method.
- Use only the specified small volume, replace the cap and keep the stock bottle away from the working area.
How to make the reasoning visible: The symbol starts the reasoning; the method reveals the route to harm and therefore the control measure.
Pictogram to practical action
Connect each symbol category to a plausible risk and a control measure. Exact control measures always come from the product label and approved method.
| Pictogram | Possible laboratory risk | Example control measure |
|---|---|---|
| Explosive | Heat, friction or impact could trigger an explosion | Avoid heat and impact; use only approved quantities |
| Flammable | Vapour or liquid could ignite | Remove flames and sparks; close the container |
| Oxidising | Fire could start or intensify near fuel | Separate from combustible material and contamination |
| Gas under pressure | A heated container could rupture | Secure it; keep away from heat; never puncture |
| Corrosive | Splash could cause severe eye or skin damage | Use eye protection, small quantities and spill control measures |
| Acute toxicity | A small exposure could cause serious poisoning | Prevent inhalation, swallowing and skin contact; teacher-controlled use |
| Irritant or harmful | Splash or vapour could irritate eyes, skin or airways | Avoid contact; use the specified concentration and protection |
| Serious health hazard | Exposure could cause long-term or organ effects | Use the specified containment and prevent exposure |
| Environmental hazard | A spill or disposal route could harm aquatic life | Contain spills and follow the instructed waste route |
A bottle has the corrosive symbol. Why does the symbol not tell you everything about the riskHow likely it is that a hazard will cause harm, and how bad that harm could be.? (Risk means how likely harm is, and how bad it would be.)
A label shows two symbols: oxidising and corrosive. Why must the method deal with both?
Choose one hazard symbol from the table. Name a control measure for it and say how it reduces the risk.
Check your understanding
Answer from memory, then check against the suggested answer.
What does a hazard symbol (pictogram) tell you?
What does the symbol of a person with a star on their chest mean?
Which symbol warns that a substance can burn skin and eyes and damage metal?
Why is “be careful” not a good safety step?
What is a hazard?
What is a risk?
A cleaning liquid has the exclamation-mark symbol (irritant). A student plans to pour a large amount quickly, above eye level. (a) How could it hurt them? (b) How could they make the method safer?
Two bottles of the same chemical have different hazard symbols. How can that happen?
Why is “be careful” not a good control measure?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
A bottle used in a practical shows two hazard symbols: corrosive and environmental hazard.
What does the corrosive symbol warn you about?
(1)What does the environmental hazard symbol warn you about?
(1)Give one way to stop it getting on your skin or in your eyes.
(1)What should you do if some of it spills?
(1)How should you get rid of (dispose of) the leftover liquid?
(1)Total for this question: 5 marks
Command word: For each symbol, say what harm it warns about, then give a safety step that stops that harm.