School Science Lessons
Laboratory safety
Updated: 2008-07-16
Please send comments to: J.Elfick@uq.edu.au
Table of contents
1.1.0 Duties of a teacher
1.6.0 Equipment safety
1.12.0 Chemicals safety
1.20 Fire safety
3.1.0 Workplace Health and Safety Act, 1995, State of Queensland, Australia
3.1.0 Bunsen burner
3.6.0 Chemical safety
3.6.5.0 Toxicity of metals and metal compounds
3.7.0 Hazards of anion compounds
3.8.0 Hazards associated with gases
3.9.0 Swimming pools
3.10.0 Toxicity, List of Poisons and First aid
Appendix 2. Information on safety issues in school-based biotechnology
1.1.0 Duties of a teacher
1.1 Supervision of students
1.2 Protective clothing
1.3 Experimental procedures
1.4 Teach manipulative skills
1.5 Live animals
1.6 Equipment safety
1.6 Test-tubes, glassware and microscope slides
1.7 Fume cupboards, fume chambers, fume hoods
1.8 Eye-washing and safety shower
1.9 Thermometers and mercury
1.10 Carbon dioxide syphon bulbs
1.11 Glass wool
1.12.0 Chemicals safety
1.12 Quantity of chemical to be used in experiments
1.13 Chemical vapours and smelling chemicals
1.14 Tasting chemicals
1.15 Handling chemicals
1.16 Storing chemicals
Chromium (VI) oxide
Sodium chlorate and potassium chlorate
1.17 Disposal of chemicals
1.18 Acids and bases
1.19 Toxicity of metals and metal compounds
1.20.0 Fire safety
1.20 Fire safety and fire equipment
1.21 Flammable liquids
1.22 Flammable gases
1.23 Combustible solids
1.24 Electrical fires
1.25 Clothes on fire
1.26 Fire prevention
1.27 Possible sources of ignition
1.28 Flammable substances
1.29 Action in case of fire
Duties of a teacher
1.0 Duties of a teacher
Teachers should select school science lessons and laboratory experiences that are appropriate to the student group and the level of learning. When selecting laboratory experiences the teacher must check that school authorities approve the activity. This document contains suggestions for practical teaching by a trained science teacher. After choosing an experiment, the teacher should practise it in the preparation room before demonstrating it to students or before requiring students to do it. The teacher has the duty of making the decision about whether the experiment is safe for the children in the classroom or laboratory. The level of risk of injury to students and teacher will vary from school to school, depending on: (a) expertise of the teacher, (b) size of the student group, (c) diversity of students, and (d) the facilities and equipment.
1.1 Supervision of students
Supervision of students must be continuous and vigilant so that unauthorized or inappropriate behaviour does not lead to accidents resulting in physical injury, fires or other dangers. Teachers must choose a set of laboratory rules to be prominently displayed and with copies given to students. Students must know the rule and understand them. Teachers must pay particular attention to the following rules:
Students do not enter any laboratory or storeroom unless a teacher is present.
Students do not eat or drink in the laboratory or storeroom.
Students do not taste chemicals.
Students must behave in a careful and businesslike manner.
Students are safely seated and not crowded, with fellow students, chemicals and glassware not within "elbow width".
1.2 Protective clothing
1. Students in chemistry classes should wear strong shoes and take care of unbuttoned long sleeves and long hair. Students must wear protective clothing, e.g. aprons, safety glasses and nitrile chemical-resistant gloves when chemicals are being handled. Teachers should be aware of students who wear contact lenses. Students wearing prescription glasses should change to use safety glasses. There is always the danger of hot or caustic materials being splashed into the eyes.
2. Many schools require students to wear heavy gloves, safety glasses (safety goggles) and closed shoes for all experiments. The four kinds of gloves are as follows:
2.1 Disposable surgical gloves, which are used during dissections, handling animal tissue and blood products, but not for chemicals,
2.2 Rubber washing-up gloves, which are not designed to protect against concentrated chemicals or organic solvents, e.g. acetone,
2.3 Nitrile chemical-resistant gloves, which are designed for handling concentrated acids and organic solvents,
2.4 Insulated heat-proof gloves.
3. Students must use safety glasses and nitrile chemical-resistant gloves if the school allows them to dilute concentrated acids or bases and when heating chemicals to avoid the danger of hot or caustic materials being splashed into the eyes. Students must wear insulated heat-proof  gloves and aprons if the activity could result in damage to their hands or body. Pay attention to unconfined long hair, jewellery, ties, unbuttoned long sleeves and loose clothing. Synthetic garments that may be a fire hazard. Students in chemistry classes should wear strong shoes that completely cover the feet and protect them from spilt corrosive or hot liquids. Students may not wear sandals.
1.3 Experimental procedures
Read the label on reagent bottles twice to avoid errors. Always follow exactly the instructions for chemical experiments. Do not substitute another chemical for chemicals specified in the experiment instructions. Always add a solid to a liquid reagent to achieve better control of gases that form in the reaction. Do not let students do unauthorized experiments. Some chemicals are safe by themselves, but they may form explosive mixtures when mixed with oxidizing agents, e.g. sulfur, sucrose (cane sugar), and powdered zinc. This document does not recommend the use of gas generators, e.g. Kipp's apparatus.
1.4 Teach manipulative skills
Teachers should teach the necessary manipulative skills by demonstration before asking students to use the skills in an experiment. These skills include heating of liquids or solids in test-tubes, heating large volumes of liquids, handling glassware containing hot liquids, carrying glassware, handling of reagent bottles. Diluting concentrated acids and inserting glass tubing or thermometers in rubber stoppers should be done by the teacher in the preparation room before the experiment.
1.5 Live animals
Biology experiments have special ethical and practical problems.
1. Students and the local community may be upset if they think animals suffer during experiments, e.g. fish and frogs.
2. Human saliva, human cheek cells, human whole blood from a hospital source, and human teeth scrapings may transmit diseases. The use of body fluids for secondary school experiments is not favoured nowadays so many laboratory experiments are now being done with artificial solutions.
3. Studies of living mosquitoes may risk transmission of malaria and other diseases.
4. Most animals can inflict bites so handle them with great care. Animal bites may transmit infections and animals may carry human parasites.
5. Treat dissection material as if it is contaminated. Dissecting instruments must be sterilized before use.
6. Vermin and the insects are attracted to animal food. Mouldy and decaying animal food and animal wastes may be health hazards because of the presence of bacteria and other micro-organisms.
7. Animals may carry parasites that could have adverse effects on humans.
8. Dissection material should be treated as though it is contaminated. All equipment should be sterile, particularly dissecting instruments.
9. Vermin and the insects, which are health hazards to both humans and the animals being kept, are attracted to animal food. Mouldy and decaying animal food and animal wastes may be a health hazard because of the presence of bacteria and other micro-organisms.
10. The teacher must answer the following questions:
10.1. Is it essential for live animals to be kept?
10.2 Have alternatives to animal experiments been investigated?
10.3 Has the number of animals been kept to a minimum?
10.4 Will the animals be housed under appropriate conditions?
10.5 Who will take responsibility for feeding and caring for animals during holiday periods?
10.6 Have procedures been established for the safe handling of animals to reduce the risk to staff and students of being bitten or scratched?
Equipment
1.6 Test-tubes, glassware and microscope slides
1. Never look down a test-tube and never point the open end of a test-tube at a student while a reaction occurs. Hold the test-tube up to the light and look from the side. Put the test-tube in a test-tube rack before putting chemicals in it. When heating substances in test-tubes, move the test-tube back and forth across the flame. Heat substances in wide test-tubes or boiling tubes.
2. When transferring materials from one container to another, hold the containers at arms length. Check glassware for cracks before use. Put broken glass metal pieces and unused chemicals in a specially marked container and bury them.
3. Microscope slides and coverslips are easily broken. Do not leave broken pieces on the desk. After each class where microscopes are used, wipe the benches with a damp cloth to remove broken glass, especially broken coverslips.
1.7 Fume cupboards, fume chambers, fume hoods
1. Do not use fume cupboards for long-term storage of any chemicals or as distribution areas for class sets of chemicals and equipment.
2. Most fume cupboards have an extraction fan mounted in the flue that conducts exhaust gases and vapours to the atmosphere. Check the extraction fan regularly. Heat-induced convection types of fume cupboards have a gas burner at the entrance to the flue to cause a rising convection current. However, these units may be fire hazards if flammable gases or liquids are placed in the fume cupboard.
1.8 Eye-washing and safety showers
Doors in and around preparation rooms are usually locked for security reasons. However, to enable access to safety shower and eye-washing facilities, ensure that connecting doors to preparation rooms are unlocked and open at the beginning of science classes. The first 30 seconds are critical in the treatment of chemical splashes in the eye. The minimum recommended time for continuation of eye-washing is 20 minutes. Remove contact lenses. For permanent eye-washing fixtures, the water stream should allow continual irrigation of the eye without harmful pressure being placed on it. You can squeeze an eyewash bottle to irrigate the eye for a short period but a continuous supply of water may still be needed when the eyewash bottle becomes empty. You should regularly empty and refill eyewash bottles to prevent contamination by algae and micro-organisms. Wearing safety glasses lessens the possibility of eye injury. Check the water pressure of safety showers or the nearest tap or hose. Where safety showers are installed, the person affected by a chemical spill should stand in the appropriate place and be thoroughly doused. Where safety showers are not installed, use the nearest tap or hose. You should check periodically permanent eye-washing and safety shower facilities. Also, check the water pressure of safety showers or the nearest tap or hose.
1.9 Thermometers and mercury
1. Thermometers supplied to schools usually contain alcohol and not mercury. Avoid leaving thermometers in containers where they are easily knocked over by students. To monitor the temperature continuously, clamp the thermometer in position. If recording the temperature at regular intervals, return the thermometer to its container between measurements. Do not leave thermometers on the desk where they may be moved by the elbows or the back of the hand. Do not place normal thermometers in the mouths of students. Do not use thermometers to stir liquids because the liquid in the thermometer may separate, making it unusable. However, you can put the thermometer in a refrigerator freezer until the liquid recombines. Do not try to recombine the liquid by heating the thermometer because it may explode.
2. Do not use mercury in school experiments. However, students may observe some of the properties of mercury by studying it as enclosed in a barometer or thermometer supplied by the education authority. Do not make a barometer or a thermometer using mercury. Mercury vapour is TOXIC and may damage the nervous system. Mercury enters the body readily by inhalation by ingestion or through the skin. If mercury is spilt from a broken thermometer, immediately pick up all the mercury with pieces of stiff cardboard, e.g. a bent playing card, or with a damp cloth or a water suction pump. Do not use a vacuum cleaner or a broom. Do not put spilt mercury down the drain. Sprinkle sulfur powder or zinc powder over the area of the spillage and collect it with a moist absorbent paper. Shine a light on the spillage to see the mercury globules. Report any mercury spill to the school authorities. Give any spilt mercury or mercury stored in the school laboratory to a government laboratory.
1.10 Carbon dioxide soda syphon bulbs
Do NOT use CO2 (carbon dioxide) soda syphon bulbs in science teaching activities, e.g. demonstration of rocketry. Use of these bulbs has resulted in serious accidents. For example, in a recent report, a student stole a carbon dioxide cylinder from a school laboratory, threw it into a fire at home and was killed by the resulting explosion.
1.11 Glass wool
Students should not handle glass wool. Thin pieces of glass wool can get into cuts and then into the blood stream. Do not touch glass wool with the fingers and do not breathe it in. Teacher and laboratory assistant may use glass wool in the preparation room but they should wear an appropriate respiratory mask.
Chemicals
1.12 Quantity of chemical to be used in experiments
In this document, "dilute solution" refers to a 2 M solution, or a 10% solution, unless otherwise specified. Also, "concentrated acid", or any other substance, refers to the concentration supplied by commercial suppliers, e.g. concentrated hydrochloric acid is 36% w / w, unless otherwise specified. For all experiments, unless otherwise instructed, use either (a) a 5 mL of solution, or (b) a test-tube filled to the depth of a finger width, or (c) the powder on a little finger nail, or (d) a piece of solid chemical the size of half a pea, or (e) no more than one third of a test-tube of any solution. Do not make gas jars full of gas for demonstration purposes. Use test-tubes with stoppers to collect gases.
1.13 Chemical vapours and smelling chemicals
See diagram 1.13
Isolate chemical vapours by doing experiments in a fume cupboard or use very small quantities of chemicals near an open window with good ventilation.
Do not inhale gases directly from the test-tube. Fan the gas towards the nose with the hand and sniff cautiously. If you detect no odour, move closer and try again.
1.14 Tasting chemicals
Never taste a chemical or any substance in the laboratory.
1.15 Handling chemicals
Students should not touch any chemical. They should use a spatula or gloves. Pipettes should be filled with a pipette-filler and not by sucking by mouth. If students do touch any chemical, they should immediately wash their hands with soap and water
1.16 Storing chemicals
1. Never return unused reagents to the stock bottles.
2. Constantly check reagent solutions and solids and replace used chemicals from stocks or stock bottles. Label reagent bottles with the name of the substance and the concentration of the solution. Never return unused reagents to the stock bottles.
3. Store concentrated acids in plastic boxes on the floor.
4. Store flammable liquids at eye level in a well-ventilated area away from heat sources.
5. Store ammonia solution (10% ammonia solution) as with acids but separate from them, not near oxidizing agents. Ammonia solution produces dangerous irritating ammonia fumes. Carefully unstopper bottles of ammonia solution in a fume cupboard to prevent damage to the eyes from the fumes. Dilute ammonia solution by adding ammonia solution to water in a fume cupboard.
6. Store formalin in glass bottles away from hydrochloric acid.
7. Store concentrated sodium hydroxide in plastic boxes on the floor but away from the acids. Do not use glass stoppers.
8. Store strong oxidants away from flammable organic chemicals.
9. Store organic chemicals inside self-sealing plastic bags. This eliminates the smell associated with such chemicals it also gives early warning of any leaking bottle.
10. Hygroscopic substances absorb water from the air, e.g. concentrated sodium hydroxide and potassium hydroxide, concentrated sulfuric acid, glycerine and ethanol ("absolute alcohol"). Deliquescent substances are hygroscopic substances that absorb water to such an extent that they form a concentrated solution of the substance, e.g. calcium chloride. Both hygroscopic and deliquescent substances may absorb moisture from tissue so treat them as potentially highly corrosive.
11. Sodium and potassium react violently with water, and the heat produced can ignite the hydrogen evolved. Contact with skin causes thermal and caustic burns. Cutting heavily oxidized potassium may cause an explosion because of the combination of the dioxide with organic material. Dispose of old stocks of potassium by dissolving the uncut lumps in propan-2-ol.
12. Powerful oxidizing agents, e.g. chlorates, peroxides, perchlorates, and perchloric acid, are not usually found in school science laboratories. Store them in a desiccator away from other chemicals. Oxidizing materials are chemicals that support combustion or burning. If they are placed in contact with materials that act as fuels, there is danger of an explosion or fire. Oxidizing materials include chlorates, peroxides, perchlorates, and perchloric acid.
Chromium (VI) oxide may cause fire on contact with combustible materials. Contact with skin causes severe burns. Spread soda ash over spillage and use plenty of water.
Sodium chlorate and potassium chlorate
Store sodium chlorate and potassium chlorate away from strong acids and any substances that are easily oxidized, e.g. sulfur, sulfides, phosphorus, sucrose (cane sugar), alcohols, organic solvents, ammonium compounds, powdered metals, oils or grease, and dust.
13. Because of constant use, reagent solutions and solids must be constantly checked and replaced where necessary from stock bottles. The reagent bottles should be labelled with the name of the substance and the concentration of the solution. Unused reagents should never be returned to the stock bottles.
1.17 Disposal of chemicals
1. Do not keep any chemicals that do not have labels or are not on a list of chemicals approved by the Ministry of Education. Ask officials in the Ministry of Education chemists or chemists in a government chemistry laboratory how to dispose of these unwanted chemicals.
2. Methods of disposal may include (a) wash to waste in a sink (b) dilute with a large volume of water, then neutralize with sodium carbonate or dilute hydrochloric acid, then wash to waste in a sink (c) add water or strong alkali and let evaporate in a fume cupboard (d) dispose with normal refuse (e) deliver to a government chemistry laboratory.
3. Do not burn unwanted chemicals because they may form carcinogenic gases.
1.18 Acids and bases
1. Prepare dilute acids by slowly adding ACID TO WATER.
2. Keep concentrated mineral acids, e.g. hydrochloric sulfuric or nitric acids, in a special container on the floor of a locked cupboard. Only the teacher or a laboratory assistant may handle concentrated acids or strong bases.
3. Wear safety glasses to protect the eyes when handling concentrated acids. Students may handle dilute mineral acids and bases, but if they spill them on the skin or in the eyes, wash immediately with plenty of water.
4. Organic acids are not so dangerous as mineral acids, but phenol (carbolic acid) and ethanedioic acid-2-water (oxalic acid) are toxic.
5. Strong bases, e.g. sodium hydroxide (caustic soda) and potassium hydroxide (caustic potash) can cause burns. Weaker bases, e.g. calcium hydroxide (limewater, slaked lime), can cause burns if they are left in contact with the skin.
1.19 Toxicity of metals and metal compounds
Toxicity is the capacity of a substance to cause harm. All chemicals should be considered as partially toxic. The toxicity of a substance is determined by the quantity of that substance required to cause harm. Risks of injury associated with any particular chemical relate directly to the route of entry, i.e. ingestion, inhalation or skin contact. A substance that may be very toxic by ingestion may be quite safe to handle if it is not ingested. Toxicity is usually reported as an LD50 oral rate, i.e. the lethal dose that will kill 50% of a sample rat population if administered orally. The following values are approximate indicators for ingestion: very toxic: LD50 < 25 mg / kg body weight, toxic: LD50 < 200 mg / kg body weight, harmful: LD50 < 2000 mg / kg body weight. The following chemicals are poisons and should never be used in a school laboratory: carbon tetrachloride (CCl4, tetrachloromethane), carbon disulfide (CS2), chloroform (CCl3) mercury (Hg, mercury metal), mercury (II) oxide (HgO, red mercuric oxide), all mercury salts, phenol (C6H5OH, carbolic acid) (white phosphorus (P, yellow phosphorus).
Fire safety
1.20 Fire safety and fire equipment
All participants in any science activity must know the location and mode of operation of fire extinguishers, fire blankets and sand buckets. Check fire extinguishers regularly to make sure they are in working condition. Check them for leakage, tampering and expiration of "use by" dates. Store fire extinguishers on the floor near the front door of the laboratory. Keep a fire blanket near the fire extinguishers. During a science class a school laboratory should have two unlocked doors. Be alert to any possible sources of ignition. Completely extinguish matches after use and put them in a non-flammable container, not a waste receptacle. Use friction or piezoelectric lighters instead of matches. Allow apparatus used during heating to cool before storage. Do not place hot objects directly on bench tops, paper or other flammable substances, but use a cool gauze mat. Do not leave hot plates, radiators and any sources of high heat unattended or left turned on overnight. Do not leave sodium and phosphorus exposed to the air. During experiments, keep away all paper, hair and flammable clothing. All personnel involved in science activities must know the position of the gas isolating valve for the room and the isolating valve at the bottled gas cylinders or gas meter. Students must not tamper with any gas fittings. Dry chemical fire extinguishers can be used on all types of fires but follow the manufacturer's instructions on the device.
1.21 Flammable liquids
Do not use any sources of ignition near flammable liquids. Low flash point substances ignite very easily and may form an explosive vapour air mixture. The following flammable liquids are allowed, if the precautions in this document are followed: ethanol, ethyl acetate, n-hexane, methylated spirit, formaldehyde solution. The following common flammable liquids are sometimes found in school chemistry laboratories but should not be used in school experiments: benzene (benzol is crude benzene motor spirit), butan-1-ol, butan-2-ol, carbon disulfide CS2, diethyl ether (C2H5)2O, cyclohexane, iso-octane, n-octane, methanol, petroleum spirit, propanol, propan-2-ol, toluene.
1.22 Flammable gases
Extinguish all sources of ignition when handling flammable gases. Turn off any Bunsen burners or better still, use electrical hot plates. For demonstrations of ignition tests of gases use only small quantities of gas. The source of gas should be closed off or be far from the demonstration. Similarly, for demonstrations of combustion of substances in an oxygen rich environment, use only small quantities of substance because the substance may flare and burn rapidly. Many propellant gases in pressure cans are flammable. Do not use carbon dioxide cylinders as a source of propellant gases. Some fluorescent lights, electrical switches and transmitting devices (radios and mobile telephones) may be sources of ignition.
1.23 Combustible solids
Most combustible solids are a fire hazard unless ground into a powder. Powders of combustible solids can be explosive when dispersed in the air. Metals in a finely divided form may ignite easily, e.g. zinc dust. Unstable solids may decompose explosively if heated or subjected to friction, e.g. potassium chlorate, sodium nitrate, potassium nitrate, ammonium nitrate, powdered metals and powdered sulfur. Strong oxidizing agents in contact with organic substances may lead to spontaneous ignition. Solids that can react spontaneously and exothermally with water or air include lithium, sodium, potassium, calcium, hydrides, nitrides, sulfides, acid anhydrides and concentrated acids and alkalis. Use only small quantities of these chemicals. Never keep them in small narrow-necked containers.
1.24 Electrical fires
Do not connect appliances or equipment whose current rating is greater than that of the power outlet. General purpose outlets (GPOs) were usually rated at 10 amps. Some GPOs may be rated at 15 amps. Do not use double adapters. Instead use portable power boards (multiple point power boards), especially those with circuit breakers. Make sure that all power leads are in good condition with no breaks or frays in the insulation, are of the appropriate current rating for the appliance being used, and are of the minimum length necessary for use.
1.25 Clothes on fire
If a student's clothes have caught fire, lay the student down, roll them over and smother the flames with the fire blanket. Seek urgent medical attention for any burns.
1.26 Fire prevention
Fires in school areas for the teaching of science may arise from chemical reactions, electrical faults, gas leakage and poor laboratory procedures. The speed with which the fire can spread will depend on the nature of the burning substances and the materials close to the fire. Fires of solids propagate slowly. Fires of liquids spread less rapidly. Gas, vapour or dust fires propagate so rapidly that they seem to explode.
1.27 Possible sources of ignition
Matches should be completely extinguished after use and placed in a non-flammable container. They should not be thrown into a waste receptacle. Friction or piezoelectric lighters can be used instead of matches in some circumstances. Apparatus used during heating should be allowed to cool before storage. Hot objects should not be placed directly on bench tops, paper or other flammable substances. A cool gauze mat should be used. Hot plates, radiators and similar sources of high heat should not normally be operated unattended or left turned on overnight. Sodium and phosphorus should not be left exposed to air. All paper, hair and flammable clothing should be kept away from flames during experiments. Gas installations. All personnel involved in science activities must know the position of the isolating valve for the room and the isolating valve at the bottled gas cylinders or gas meter. Students must not tamper with any gas fittings.
1.28 Flammable substances
Flammability varies with the ease with which a solid, liquid, vapour or gas will ignite easily and burn rapidly. There are many factors used to measure flammability such as ignition temperature and flash point. The following are descriptions of various degrees of flammability: (a) Highly flammable substances have a very low boiling point, form vapours easily at room temperature and are easily ignited. (b) Flammable substances have a higher boiling point, form vapours less easily and require a higher temperature for ignition. (c) Combustible substances do not form vapours easily at room temperature and require a much higher temperature for ignition.
1.29 Action in case of fire
Evacuation: If a fire should break out in an area for the teaching of science, the students must be moved from the source of the fire and evacuated, if necessary. A whole school evacuation may be necessary. Observe the school's evacuation procedures, including contact with the fire brigade. Besides the school fire drill, science classes should practice a special fire drill for the laboratory.