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Smoke detectors in science lab

Discussion in 'Science' started by doublehelix, Jan 20, 2011.

  1. I'm hoping for advice from knowledgeble colleagues.
    I was burning magnesium in my newly-completed science lab. Just a few cm ribbon but it made enough white smoke to set off the fire alarm. The whole school was evacuated.
    I was under the impression that science labs should not have smoke alarms. Is that correct? Perhaps someone could point me towards the correct, authoritative, source of information.
    Also, is there a specific problem concerning smoke from magnesium? I have burned other substances, producing smoke, without triggering the alarm. Perhaps the particle size of magnesium oxide is such that it triggers smoke alarms more easily than other smoke.

     
  2. I'm hoping for advice from knowledgeble colleagues.
    I was burning magnesium in my newly-completed science lab. Just a few cm ribbon but it made enough white smoke to set off the fire alarm. The whole school was evacuated.
    I was under the impression that science labs should not have smoke alarms. Is that correct? Perhaps someone could point me towards the correct, authoritative, source of information.
    Also, is there a specific problem concerning smoke from magnesium? I have burned other substances, producing smoke, without triggering the alarm. Perhaps the particle size of magnesium oxide is such that it triggers smoke alarms more easily than other smoke.

     
  3. We had a similar problem in refitted Science rooms. We had the smoke alarms replaced with heat detectors with no further problems. The first time we set the alarms off the Fire brigade stayed to watch the thermite reaction.
    You could try Cleapps for advice.
     
  4. blazer

    blazer Star commenter

    I evacuated the school a couple of years back with the screaming jelly baby demo!
    Downstairs rooms should have some sort of fire detection. However in labs it should be heat detectors not smoke detectors. The people that installed ours were supposed to install heat detectors but put smoke ones in by mistake! No-one noticed until the day I set it off then it was realised and they came in next week and replaced it! I checked then and was told that the detector will only go off if it detects a large, hot, sustained heat source so it will not go off if you have 15 bunsens on nor does it go off when I demo the burning coffee whitener! I suppose we won't find out if it really works until I set the bench alight!
     
  5. phlogiston

    phlogiston Lead commenter

    Glad I'm not the only one. I was showing some year 11 why ammonium nitrate wasn't on sale in Northern Ireland! Also a sixth former inadvertently heating the rubber bits on a clamp.
    Best wishes,
    P
     
  6. Sadly it's not just inside Science labs, they installed a smoke detector RIGHT OUTSIDE of a lab, rule number one when doing most practical tasks - keep the room well ventilated. Door open after practical smoke leaves alarm goes off... I'm moving into a new build lab soon, maybe I should check this before hand.
     
  7. briggs1209

    briggs1209 New commenter

    had the same problem ten years ago when they built us a new suite of labs, first week of term and the alarms all went off. First they just taped up all the smoke alarms in the labs - that just meant the corridor alarms went off instead when we opened the doors at the end of the lesson. Eventually they were replaced with heat alarms.
     
  8. I don't blame them! I did this with my Y9's the other day and it was great!
     
  9. Thanks for the support everyone. Nice to know I am not the only one. Pity the 'powers that be' don't think to consult.
     
  10. paulie86

    paulie86 New commenter

    We had same problem in my block of flats! They have all had to be changed to the heat detecting ones. Slight wiff of burnt toast in someones flat and everyones alarms were going off!
     
  11. We had this problem at my previous school.
    The only way around it was to either cover the detectors for that lesson and then remembering to uncover them afterwards.
    And/or informing the school office that there would be a chance of them going off and they could cancel any false alarms before the whole school turned out.
    Of course this had to be OKed with the H&S officer before we could do it.
     
  12. blazer

    blazer Star commenter

    Or alternativly get the school outside three times a week until they replace them with the correct detectors!
     
  13. We have a fairly new building with smoke alarms in all the labs, to overcome the problem of the smoke alarms going off if burning materials in the lab we have covers (bright orange in colour) that fit over the alarms - unfortunately some of the labs ceilings are too high even to reach with a normal set of steps. We also inform the site manger if we are doing anything that could set off the alarms (so far in 2 years we have had 3 alarms go off - 2 for science and one in food tech).

     
  14. blazer

    blazer Star commenter

    Surely though if you are carrying out an activity (such as cooking) that could result in a fire you should not disable the alarm system?

    W had a fire inspection a few years back from the Fire Brigade. They wanted to close the school down (in fact they wanted to close most of the schools in Birmingham down) because our fire precautions were not up to spec.

    We spent £300,000 over the next 3 years to put in place their recommendations. This included fire detection equipment in all ground floor rooms that had rooms above (Most of our school is single storey but there are some bits that are 2 storey). This was ensure the safety of people working on the first floor outside of normal school hours. The reasoning, we were told, was that during a normal day a fire would be spotted quickly and the alarm raised. However once school finished and the vast majority of people had left anyone working upstairs would not be aware if a fire broke out in a room below them as there would be no-one around to raise the alarm. My understanding was that these fire detection devices were only activated outside normal school hours. But this isn't the case. They are on 24/7. So 2 of our labs have heat detectors as they are on the ground floor with classrooms above. The other 3 labs do not need them as they are on the first floor.

    Since they have replaced the smoke sensors with a heat sensors we have not had any false alarms from them. They are pretty redundant during the day anyway as I was told by the installer that there would have to be quite a large, sustained and very hot heat source to activate one, I think I would notice if there was a raging inferno in the corner of my lab!

    A large part of the money we spent was improving existing fire doors, installing loads more fire doors and also replacing doors to stockrooms, offices and other non-teaching rooms with doors with windows so that you can check inside before you go in! These doors cost hundreds of pounds each and installation is also very expensive.
     
  15. ryeland

    ryeland New commenter

    Seems a common problem - I remember starting at a new school and being told that under no circumstances was magnesium to be burnt by pupils - smoke alarm in the labs. It was a fume cupboard demo, so sad.
     
  16. TCSC47

    TCSC47 Lead commenter

    I got hold of a portable fume cupboard for demos producing smoke and fumes. Being portable it can be placed in the most advanteous position for the class to observe the demo. Built in fume cupboards are useless for the large classes that have to be taught nowadays.
    The burning of magnesium has to be carried out behind a screen nowadays. Anything less will result in an official warning. Simples.
    Whilst magnesium oxide is harmless in itself and found in indigestion tablets, the fumes can still cause a problem from irritated lungs and wheezing. I don't know how this would relate to a limited exposure to the class, but the problem has been well researched and documented in welding, where magnesium oxide fumes have been shown to cause "metal fume fever". So if your students ever have any respiratory problems from the demo, you would be considered culpable because you would be expected to know this.
    Cheers.
     
  17. blazer

    blazer Star commenter

    Do you know why there are no sciencist in this country over the age of 40? because we all died years ago from Mg, Hg and all the other stuff that we used to bathe in in the days when science was a fun subject and enjoyed by students. Now it is just all virtual practicals and cut and stick. No wonder the kids hate doing it!
     
  18. What now? Smoke detectors in fume cupboards?
     
  19. phlogiston

    phlogiston Lead commenter

    We have a couple of labs with toy mobile fume cupboards. Totally useless except as a 4 sided safety screen or cointainment vessel for a screaming jelly baby. I did a lead bromide electolysis in one last year and hed to terminate because of the bromine fumes going straight back into the classroom.
    P
    Interesting points about Mg.
     
  20. Any teacher of science , let alone chemistry, who is told (off the cuff) you mustn’t do this or do that, should contact CLEAPSS or SSERC (in Scotland) for a definitive answer. To be told by Head teachers, Ofsted/ISI Inspectors, Insurance Safety inspectors, Bursars, HODs who are non specialists, Technicians even, that you cannot do a certain activity (which has been done many times before) needs to be examined critically before you dash down a comment to the TES to worry other teachers. There will be many teachers who burn magnesium in their laboratories with no problems who will now think they are doing something wrong and stop doing it. This is how myth and rumour start.
    Smoke detectors: Building Bulletin 80 (dating from1999 and in the second edition 2004) from the then Department of Education says they should NOT be installed in laboratories. If you cannot convince the Bursar by argument, get them to phone the advisory organisations or their local safety education advisor (if not made redundant by now). Read the supplementary risk assessment for the howling jelly baby and you see the problems caused by placing this experiment in a fume cupboard. Fume cupboards are primarily designed for toxic gases not sudden gusts of ‘smoke’ (it is mostly water vapour).
    The statement on magnesium: Whilst magnesium oxide is harmless in itself and found in indigestion tablets, the fumes can still cause a problem from irritated lungs and wheezing. I don't know how this would relate to a limited exposure to the class, but the problem has been well researched and documented in welding, where magnesium oxide fumes have been shown to cause "metal fume fever".
    Please if you don’t know, contact organisations that do! Magnesium oxide has a Workplace Exposure Limit (WEL) of 10mg per metre cubed AVERAGED OVER AN 8-HOUR PERIOD. Ten seconds in a school laboratory would be well below that level. You don’t require safety screens either. The WEL is in place to protect welders not to stop teachers showing this reaction.
    There is a difference between Hazard and Risk.
    Filter Fume Cupboards: I have made chlorine and reacted bromine in many filter fume cupboards and there have been no leaks. Something is wrong with the machine if there is. CLEAPSS and SSERC may even be to offer advice on this.
    Worries over biology issues (dissection) and physics (radioactivity and high voltages) can also be addressed.
    Please: let us return to showing pupils just how fantastic science is. I think I will contact the advisors at to CLEAPSS or SSERC to see if any of you have phoned up or emailed them!
     

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