Personal experiences of accidents in secondary science

Risk assessment and risk management

This blog post is an account of accidents which I have direct or indirect experience of, either because they occurred in my own lessons or training sessions, or because they happened to colleagues.  The rationale for the post is to reflect on my own learning from these events, and to consider firstly how things can go wrong, and secondly how the impact or seriousness of these things can be lessened.  Essentially this is about what is called risk management, the companion to risk assessment.  What's the difference?  Both are concerned with thinking about risk.  I would say that risk assessment relates to the thinking about risks involved in a procedure before that procedure happens.  Risk management on the other hand is the thinking you do while the procedure is happening, a vigilance in which you are constantly alert to the possibility of something going wrong, and acting to ensure that if it does, the severity of the consequences are minimised.  It is important to make the distinction between risk assessment and risk management:  by referring to risk assessment only, we may unwittingly give the impression that being careful enough before the event is sufficient.  It's not.   Some people may use the term risk assessment as an umbrella term for all of this; what phrase we use is not the point – it is that we are thinking about hazards and risks before, during, and in some cases, after, the event. 

Most of the accidents described below happened during chemistry activities; this could be ascribed to my chemistry specialism and the fact that I have taught more chemistry than biology or physics.  However, chemistry at school is arguably a more hazardous enterprise than biology or physics.  Fortunately most of them did not result in any serious injuries.  This is partly because of luck, but also because of the degree of risk management used.  It is certainly not intended to promote complacency.  Although the number of incidents recounted here may seem like quite a lot, they occurred over a long time period, reflecting the fact that accidents in science lessons are fortunately rare.

Accidents with the Thermite Reaction

The thermite reaction is in a class of its own as far as demonstrations go, partly because of the spectacle, and partly because of the very real danger involved.  The currently recommended method from CLEAPSS is to perform it in a fluted filter paper over a one litre beaker of water and sand.  This is so that the biggest hazard, the molten iron produced, falls through the filter paper into the water and is removed as quickly as possible.  If this method is not used, the red hot liquid iron remains in situ and cools gradually.  I've had two accidents when I've not used the CLEAPSS water method.  Both were avoidable, which is usually the case with accidents. 

Forgetting to use sand for insulation

The first mishap was when I performed the thermite reaction on two heatproof mats, forgetting to use a tray of insulating sand.  This was just a very careless thing to do, although it demonstrated to me the limits of 'heatproof' mats.  The molten iron went through them both very easily, and also made an admirable charred pit on the wooden science bench.  It was a very run-down room and the bench was very well-used, so my little mishap didn't make a major cosmetic difference, but I felt somewhat stupid for forgetting what is a rather basic but vital safety aspect of the demonstration.  Fortunately, there were no other consequences of this, and nobody was hurt, because I'd remembered the other precautions.  It was simply a lesson in remembering to use adequate insulation.

Escaping molten iron

The second incident with the thermite reaction occurred when I was carrying out some training for science teachers.  I was performing the reaction on a tray of sand - which I'd remembered this time.  The bonus of this method of the demonstration is that the reaction mixture stays spectacularly hot, and this can be felt from a distance of a few feet.  It is something of a 'wow' factor when people can feel this by holding their hands out and sensing the radiant heat from a distance.  My usual technique was, in the immediate aftermath of the reaction, to pick the fused lump of glowing material with a pair of tongs and bring it to the audience so they could experience this radiant heat (from a safe distance, still).  On this occasion the accident was that the red hot molten iron, which is always at the core of the lump, found its way to the outside and proceeded to drip out on to the floor, leaving some charred streaks.  Now this was relatively minor, but the implications could have been far more serious had I not been managing the risk, which I was doing.  The risk was that material being dropped from the tongs could burn someone.  In light of this, the golden rule is that the tongs should never be held over someone - for instance over their legs if they are seated.  Hence, in this accident the only things that was damaged was the floor, not people.  Since this incident however I've always just followed the CLEAPSS method and removed the hazard virtually as soon as it forms.

Accidents with the alkali metals

I have, fortunately, never had an accident with the alkali metals.  However, I have witnessed one, and I know of two others which colleagues experienced, one of which was pretty serious.  It's interesting to note that all of these incidents involved sodium, which despite being less reactive than potassium seems to have a greater propensity for causing things to go wrong, perhaps because we think it is somehow a less serious hazard.

Using too much alkali metal

The accident I witnessed personally was a salutary reminder of why small pieces of alkali metal are used when demonstrating the reaction with water.  I was standing nearby when a teacher put a 1cm3 piece of sodium into a water trough.  I had barely uttered the words, "I think that was a bit big..." when the piece exploded violently with a loud bang.  The molten sodium produced by the heat of the reaction spread over surrounding surfaces, including on to an LCD projector attached to the ceiling above.  Fortunately, there were no injuries.  Why would a teacher do such a thing as this?  There is only only reason - he was showing off.  The event was a 'train the trainer' day run by the Royal Society of Chemistry for prospective trainers on one of their professional development programmes.  The teacher in question was not subsequently invited to work as a trainer, but hopefully he learnt something from the incident.  The advice on the size of pieces of sodium or potassium to be used in this demonstration is 'a grain of rice'.  I usually cut a piece which is difficult to compare to this because grains of rice are long and thin, and often the lump of metal cut off a larger block is more cubic.  My own version of the size is 'a petit pois' (one of those tiny peas). 

Spitting sodium

The second incident happened to a teacher colleague during his demonstration of sodium reacting with water.  A tiny piece of sodium spat out of the water trough and landed, unknown to him, on his scalp.  Seconds later he felt an intense pain as it burnt him.  The message from this is that sodium can spit when it reacts with water, and the current accepted method for the demonstration is to actually put the safety screen over the top of the trough so that the risk of injuries such as this one are avoided.

Using alkali metals for another procedure

The third incident was recounted to me by a colleague who had had an accident with the alkali metals during the 1980s.  It was sufficiently serious to have made it into the local newspaper, which is not an outcome any teacher wants.  Unfortunately, it was his own lack of sufficient knowledge and awareness which was the cause of this, although ultimately the responsibility lies with the school for failing to provide him with adequate guidance.  He was using the reaction of sodium with water, not to demonstrate this reaction, but to demonstrate the production and collection of hydrogen gas.  There are standard methods of producing and collecting hydrogen gas, but this isn't one of them.  This is because of the risk that a spark from the reaction will ignite the hydrogen.  This is basically what happened in this case.  The gas was being collected in a glass gas jar, which proceeded to act like an air-borne missile, describing an arc through the air before hitting the floor and shattering near to pupils.  In the meantime the water, which had become a potentially hazardous solution of sodium hydroxide, splashed the pupils.   Again, fortunately no pupils were seriously injured, but the incident is another lesson to be learned.  Whether the inclusion in the local paper was warranted is questionable, but this is beside the point once it has happened.

Things that have caught fire

I've had to use a fire extinguisher three times in a school, two of which were for fires in teaching laboratories.  The third was to extinguish a fire on some dry grass on the school field; I'm not recounting this one in detail here as there is little more to tell.  There are a couple of other instances which I've included in this section however. 

Leaky reflux equipment

The first time I had to use a fire extinguisher in class was during an 'A' level chemistry procedure, in which a student had a leak in their glassware during a reflux procedure involving a flammable solvent.  We didn't have electric heating mantles for such operations, so we had to use Bunsen burners, and consequently the solvent caught fire.  It wasn't a serious fire, but the student was a little shaken as his attempts to waft and blow the fire out were unsuccessful.  I used the carbon dioxide fire extinguisher in the lab and the fire was swiftly extinguished.  No harm done.  My own learning from this is that I always make sure I know where the fire extinguisher is if I'm working in a lab - sometimes it might not be in the room but outside on the corridor. 

Spirit burners - Molotov cocktails, basically

The other incident where a fire extinguisher was called for was a class practical with a year 9 class in which they were using spirit burners to heat water and calculate the energy transferred.  Spirit burners are a widely known hazard because they are in principle no different to petrol bombs - they just contain a flammable alcohol rather than petrol.  Hence a lit spirit burner is dangerous because if it is dropped or knocked over then a fire is the highly likely result.  This happened in my lesson - a spirit burner ended up on the floor and there was then a small puddle of burning fuel under a lab stool.  If not dealt with this can then spread to things like coats or bags, if they are nearby.  Again I was able to quickly grab a fire extinguisher and deal with this fire. 

Tackling fires is something that should not be taken lightly.  In both incidents described above these were small fires which had not been burning long, and there was no significant risk to anyone nearby, nor to the school.  Hence there was no need to sound the fire alarm, or take any other action.  In both cases I knew what was burning, and I knew that the carbon dioxide fire extinguisher was suitable to use (although there was no other option).  If these had not been the circumstances, then there might have been a need for more serious steps, such as sounding the alarm. 

Fuel flashover

I had another incident which I'm including in this section even though there was no fire to extinguish - this was what is commonly called a 'flashover' - a sudden ignition of a fuel/air mix.  I was demonstrating the burning of the fractions produced in the fractional distillation of crude oil, which I had performed just minutes before.  I was performing this as a demonstration so had the class seated, watching as I carried out operations behind the teacher's desk.  I poured the fractions into evaporating basins and ignited them with a lit splint so the ease of ignition and flame characteristics could be observed.  As there was a reasonable quantity of each fraction I was not letting each one burn out, but instead was extinguishing each one with a heatproof mat after we'd observed it sufficiently.  I was on to probably the third or fourth fraction, and was lighting the splint for the next one, when there was a sudden unexpected ignition and flame which momentarily covered virtually the whole desk.  The pupils thought this was brilliant, but I was somewhat taken aback as I'd clearly missed something important. 

I'm pretty sure that the event was caused by my extinguishing of the flames before the fractions had finished burning.  What was happening during the burning was that the container, an evaporating basin, was getting hot.  This heat energy was then causing the remaining unburnt fraction to continue to slowly evaporate after the flame had been put out.  Over a few minutes a sufficient quantity of this highly flammable fuel vapour had clearly formed and was, unbeknown to me or the pupils, sitting on the desk ready to ignite with the next naked flame.  Whenever I perform this demonstration now I always use a small enough amount of the fractions so that I can burn the entire amount and there is no risk of leftover vapour.  I usually do it in a fume cupboard too.

Not disposing of material appropriately

There is a nice little practical experiment that pupils can do called 'magic writing' in which they 'paint' a saturated solution of potassium nitrate on to absorbent paper (like sugar paper or a paper towel), let it dry (or dry it with a hair dryer) and then touch it with the end of a red hot piece of wire.  The energy initiates an oxidation reaction which burns out the painted bits of paper, leaving the rest unscathed.  Potassium nitrate is an oxidising agent, meaning that it will support combustion by supplying oxygen right where it is needed. 

This incident occurred after I'd used this procedure on a training course for science teachers, in a school.  The course had finished, the technician had cleared everything away, and I was on my way home.  The bits of paper from the 'magic writing' experiment had been bundled together and put in a bin in the prep room.  They should, instead, have been thoroughly soaked in water before placing in a bag in the bin.  Overnight, somehow, these pieces of paper began a smouldering fire in the bin.  Whether it was that one of the pieces scooped up had still got a minuscule glowing remnant on it we cannot be sure, but the fact is that it somehow kindled a fire.  Fortunately the fire did not get out of control - indeed it probably remained fairly localised, but the next morning the smoke damage was evident.  Although the responsibility for disposing of this material had not been mine, it nevertheless taught me that one cannot assume someone else will know about things like disposal of something like this, which probably seemed fairly innocuous.  I now always check that people like technicians know about appropriate disposal of materials after chemistry lessons.  Technicians perform an essential role in school science departments, but we shouldn't assume they have a comprehensive knowledge of every procedure or every risk.  Making sure we work together we can all learn better to avoid things like the incident described here.   

Chemicals in the eye

There is a very important general rule in chemistry relating to eye protection, which is that alkalis will cause more serious damage to eyes than acids.  I've had a small number of incidents in lessons in which pupils have received small amounts of chemicals in their eyes, fortunately none of them alkalis. 

Acid in the eye - even with the stopper on the bottle

This incident is one of the main health and safety stories which I tell to illustrate the reasons for following guidance - in this case to wear eye protection.  It happened to a year 7 boy at the start of a practical experiment involving dilute acid (probably 1M, although I forget the exact concentration).  I had gone through the procedure with the class, including the need to wear eye protection, and they had just started getting equipment from around the room to take to their desks.  I'd noticed that a small number of them had not in fact followed my instruction to wear eye protection, and was just in the process of making a general announcement to this effect when a boy began calling out that he'd got acid in his eyes.  I initially thought that this was his little joke as it was timed perfectly to follow my announcement.  However within a split second I realised he wasn't messing about.  I quickly grabbed him and escorted him as safely as I could to the sink where the eye-wash facility was.  There is no time to lose when pupils get something in their eyes like this, so I had to put his head in the sink and run the water over his eyes.  Of course the difficulty is that there is a natural tendency to close the eyes, so the process takes time and the injured party has to be coaxed into opening their eyes so the offending chemical can be flushed out, which it ultimately was.  He could continue with the lesson afterwards.

How had this accident happened?  The primary reason was that the boy had not been wearing eye protection.  However, the secondary causes are that he had not thought this was important at the time because he had just been carrying the stoppered bottle of acid to his desk and hadn't actually begun the experiment.  This was his undoing.  On getting to his desk he realised that he needed to clear some of his things out of the way to make space for the experiment, so he'd put the bottle down on his stool, an action that required him to bend slightly as the stool was obviously lower than the desk surface.  Bending brought his eye into vertical alignment with the stopper which, as he placed it quite hard on the stool, popped off, and a drop of acid then splashed out, upwards and into his eye.  So, although he thought he was safe as the stopper was on the bottle, this just goes to show that accidents have a way of happening in the most unexpected ways. 

Crystals in the eye requiring a trip to hospital

This accident happened to a teaching colleague.  It is another example of accidents happening when we least expect them.  I don't know what the crystalline substance involved was, but it was in a container on a shelf slightly above head height.  As the teacher pulled it off the shelf there must have been some jarring movement which caused the lid to come off, and the jerk then propelled some of the crystalline contents out and downwards into my colleague's face.  He ended up with crystals in his eyes and had to be taken to hospital for medical attention.  The risk from this sort of thing is that the crystals will scratch the delicate surface of the cornea, leading to complications such as eye infections which could affect or even jeopardize one's eyesight.  Fortunately he was OK.  There are some points of relevance here.  One is about the risk to eyes from solid substances - we tend to think of liquids when we need eye protection.  The second is the issue of things stored above head height, which always carries a risk, no matter what it is.  

Malfunctioning equipment

Fume cupboard venting into the lab

The main example of malfunctioning equipment causing a problem occurred while I was on teaching practice as a trainee teacher.   I was performing a demonstration of the reaction of aluminium powder with iodine crystals, a visually exciting spectacle that produces clouds of purple iodine vapour as well as sparks and flames.  It is necessary to perform this demonstration in a fume cupboard because of the iodine vapour, which billows off the reaction in dense clouds.  I’d set the reaction up correctly on a watch glass placed on a heatproof mat, but I was not aware that this particular fume cupboard was not working properly - indeed I assume nobody else knew this as it should have been out of use with a sign on it.  Instead of extracting the purple clouds to the outside of the building, they were instead being channelled out of the top of the fume cupboard and into the lab.  It was the pupils who first spotted this, and decided they weren't going to stay in the room in case they choked.  This was somewhat embarrassing for me of course, to be nominally in charge of a class who had taken themselves out on to the corridor as a rather noisy and excited crowd.  However, it was ultimately the right thing for them to do.   We opened the windows and ventilated the lab, and resumed the lesson a few minutes later.  My learning from this event is to always check the operation of fume cupboards before I use them.

General accidents

Glass teat pipette piercing a hand

I have forgotten the exact practical experiment which was being carried out when this accident occurred.  It was a relatively non-hazardous one, but illustrates that accidents can occur even in activities like this.  Whatever it was, it required the use of teat pipettes, and the ones supplied by the technician were glass ones with fairly long tapering nozzles.  Somehow a girl in the class managed to pierce the fleshy skin between her thumb and first finger with this.  I’m pretty sure this was not a ‘misadventure’ – she was a very sensible girl who wouldn’t have been messing around.  The first I knew of it was when her friend came to me in a state of some agitation to tell me what had happened.  After ascertaining the girl was OK I instructed her friend to escort her down to the school nurse to have her injury looked at.  She was fine.  The sting in the tail of this story is that the friend, who had clearly been disturbed by the incident, perhaps by the sight of blood or seeing the pierced hand, then fainted on the corridor.  Fortunately, again, she was OK.  A lesson to be learnt about how some pupils might be affected by others’ misfortunes. 

Near-misses

The wrong use for eye protection

There is an unfortunate irony about personal protective equipment (PPE).  It is that by protecting us from harm we don’t get to experience the effect the hazard can have, and therefore we may fail to appreciate the importance of using it, or even come to see it as a tedious regulation.  Certainly there are cases in which the need for PPE is debatable, but good risk assessment should minimise this.  The incident I’m recounting here is of a pupil totally failing to think about the purpose and importance of eye protection; though there are implications for the management of the practical activity. 

The activity in question was the reaction of metals with either acid or water.  Pupils had test tube racks and test tubes to put the acid or water in, and metals were placed around the room for them to collect and put in the test tubes.  This was actually poor risk management on the part of the teacher, not just because one of the metals was calcium, a metal that presents some particular hazards, but also because there was no provision or guidance on what to use to carry the pieces of metal.  It was perhaps presumed that pupils would realise they needed to take their empty test tubes to each metal in turn – a somewhat poor expedient, but the only one that would have been possible given the activity set-up.  I was in the room as a support teacher, so hadn’t had any part in this.  This particular pupil was in some ways using his initiative, because he was using his goggles as a receptacle for carrying the pieces of metal to his desk.  I intercepted him as he was doing this with the calcium.  I gave him a serious telling off, which was perhaps a bit unfair, but I wanted him and the whole class to recognise the danger in this little enterprise.  Had any small piece of calcium lodged in a crevice in the goggles, which was entirely feasible, then it could equally have become dislodged when someone put the goggles on and ended up on their face or even worse, in their eye.  Calcium in the eye could cause permanent damage because when it gets wet it gets hot enough to burn skin, and would burn eye tissue very easily.  There were two real problems here, however.  One was that the teacher hadn’t provided an alternative for pupils to carry pieces of metal to their desks.  The second was that there was an inadequate culture of health and safety in science lessons.  Goggles were in poor condition – scratched and with stretched or perished elastic – and were tossed into trays at the end of each use.  They were basically not fit for purpose.  Pupils had probably become accustomed to them as a regulatory feature of practical work, but did not appreciate their importance. 

Christmas tree lights from home

Many years ago my year 9 form group wanted to decorate our form room at Christmas time.  As this room also doubled as a science lab (albeit a very archaic and run-down one) I had to quash their ambitions a little, but I consented to one of them bringing an artificial tree and some lights from their home.  When they brought this in I was glad that I was there before they attempted to plug the lights into the mains.  This was in the days when Christmas tree lights plugged straight into the mains, unlike today when the lights are connected to a transformer which steps down the voltage.  The twin strands of flex each had a bared section with the mains wire visible and easily touchable.  The thing that shocked me was that this child’s parents would have allowed their child to bring this potential death-trap into school – although perhaps they didn’t know.  Obviously I had to forbid the use of the lights, and explained to the crestfallen class why we couldn’t use the lights.  There is a lesson here in being very careful and cautious about anything a child brings in from home.  One cannot guarantee that they know the full extent of what they are bringing, nor its safety.