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Chemistry labs are among the safest places in a school, largely because everyone follows the same rules every time. Most accidents happen when someone decides a rule doesn’t apply “just this once”. Knowing why each rule exists makes it much easier to follow them without thinking.
Here are the rules that apply in nearly every chemistry lab, grouped by topic, with the reasoning behind them. Your own school or college will have its own rules too, and those always come first.
Before you start
1. Read the method and the risk assessment first. Know what you’re going to do, which chemicals you’ll use, and what their hazards are before you touch anything. Surprises cause accidents. See how to write a risk assessment.
2. Know where the safety equipment is. Find the eyewash station, safety shower, fire blanket, fire extinguisher, first aid kit, gas shut-off and exits on your first day. In an emergency, there’s no time to look.
3. Only do experiments that have been approved. Never carry out unplanned experiments or mix chemicals “to see what happens”. Some combinations release toxic gases or react violently.
What to wear
4. Wear eye protection whenever chemicals, glassware or heat are in use. Eyes are the most vulnerable part of your body in a lab. Splashes, flying glass and spitting liquids can cause permanent damage in a fraction of a second. Keep goggles on until everyone has finished and cleared away, not just until your own experiment is done.
5. Wear a lab coat, fastened. It protects your skin and clothes from splashes and can be removed quickly if contaminated.
6. Tie back long hair and secure loose clothing, scarves and jewellery. Loose hair and sleeves can catch fire in a Bunsen flame or dip into chemicals.
7. Wear closed shoes. Dropped glassware and spilled chemicals are a real risk to feet in sandals.
8. Wear gloves when the risk assessment says so. Gloves protect against corrosive and toxic chemicals, but they’re not needed for everything. Remove them before touching door handles, phones or your face, and choose the right material for the chemical.
How to behave
9. Never eat, drink or chew gum in the lab. Food and drink can pick up chemical contamination. Many poisonings happen by mistakenly tasting or swallowing something.
10. Never taste chemicals, and don’t smell them directly. To detect an odour, waft a small amount towards your nose with your hand.
11. Walk, don’t run, and keep bags and coats out of the way. Trips and collisions near open chemicals and hot equipment are a common cause of injury.
12. Keep your bench tidy. Clutter means knocked-over bottles and missed hazards. Only have out what you need.
13. Never work alone. If something goes wrong, someone needs to be there to help or call for help.
14. Report every accident, spill or breakage, however small. A small cut from glass may contain chemical contamination. A tiny spill left behind can harm the next person.
Handling chemicals
15. Read every label twice. Check the name and the concentration before using a chemical. 0.1 mol/dm³ and 2 mol/dm³ hydrochloric acid look identical but have very different hazards. Learn the GHS hazard pictograms.
16. Take only what you need, and never return unused chemicals to the stock bottle. Returning chemicals risks contaminating the whole bottle.
17. Keep lids on bottles. Replace stoppers and caps immediately to prevent spills, evaporation and mix-ups.
18. Use a pipette filler, never your mouth. Mouth pipetting has caused serious poisonings and burns.
19. Always add acid to water, never water to acid. Diluting concentrated acids releases a lot of heat. Adding water to acid can make it boil and spit. See handling acids and bases safely.
20. Use a fume cupboard for anything that gives off harmful fumes. Fume cupboards pull vapours away from your breathing zone. Keep the sash as low as practical.
Heating
21. Point test tubes away from yourself and others when heating. Liquids can suddenly boil and shoot out (“bumping”).
22. Use the right Bunsen flame. Use the yellow “safety flame” when the burner is lit but not in use, so it’s visible. Use the blue flame for heating. Turn off the gas when you’ve finished.
23. Never leave a flame or hot plate unattended.
24. Keep flammable liquids away from flames. Ethanol, propanone (acetone) and other solvents catch fire easily. Their vapours can travel along a bench to a flame.
25. Remember that hot glass looks exactly like cold glass. Let equipment cool before handling, and use tongs or heat-resistant gloves.
Glassware
26. Check glassware for cracks and chips before use. Damaged glass can break under heat or pressure.
27. Don’t force glass tubing or thermometers into bungs. Broken tubing causes deep cuts. Ask for help if it’s stuck.
28. Clear up broken glass with a brush and dustpan, never your hands, and put it in the glass waste bin.
Electrical equipment
29. Keep water and chemicals away from electrical sockets and equipment.
30. Check cables for damage before use, and switch off at the socket before connecting or disconnecting.
In an emergency
| Situation | What to do |
|---|---|
| Chemical in the eye | Rinse at the eyewash for at least 10–15 minutes (longer for alkalis); get help immediately |
| Chemical on skin | Rinse with plenty of cold running water for 10–20 minutes; remove contaminated clothing |
| Minor burn from heat | Cool under running water for 20 minutes; tell the teacher |
| Clothing on fire | Stop, drop and roll, or smother with a fire blanket; use the safety shower if available |
| Small fire in a container | Cover with a heat-resistant mat or fire blanket to cut off oxygen; turn off gas |
| Swallowed a chemical | Rinse the mouth, don’t induce vomiting, get urgent help |
| Gas leak | Turn off gas taps, no flames, open windows, tell the teacher, evacuate if needed |
Clearing up
31. Dispose of waste as instructed. Some solutions can go down the sink with plenty of water; others, such as heavy metal solutions and organic solvents, must go into labelled waste containers.
32. Clean and return equipment, wipe down the bench, and wash your hands. Washing hands at the end removes traces of chemicals you might not notice.
Why the rules work
Almost every rule follows one of four principles:
- Keep chemicals out of your body: eyes, mouth, skin, lungs.
- Keep energy under control: heat, flames, pressure and electricity.
- Know what you’re working with: labels, risk assessments, plans.
- Be ready for things to go wrong: know the equipment, report incidents, never work alone.
If you remember the principles, you can work out the right thing to do even in situations no rule covers.
Key takeaways
- Wear eye protection whenever chemicals, glass or heat are in use, and keep it on until everyone has cleared up.
- Read labels and risk assessments before starting, and only do approved experiments.
- Never eat, drink, taste or directly smell chemicals in the lab.
- Add acid to water, use pipette fillers and fume cupboards, and never leave flames unattended.
- Know where the safety equipment is, and report every incident.
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