Learning by Accident

««« Submitted by STAO Members in Region 3 and 4.

Learning by Accident is an ongoing Crucible feature, in which real-life lab accidents or incidents are recounted and explained. The goal is to highlight the consequence of ignoring safety rules so that science educators will be further encouraged to become knowledgeable, and to take appropriate action, in areas of safety that affect their daily activities in the science classroom. Submissions are encouraged. If requested, anonymity will be guaranteed. Please send written descriptions to Ian Mackellar, STAO Safety Committee Past-Chair, Box 191, MAITLAND, ON K0E 1P0

A Hot Situation!
During a laboratory practical activity, supervised by a supply teacher, a student lit the gas at the gas tap producing a flame of 1 m in length. Acting in haste, the supply teacher turned on the adjacent gas tap, resulting in two gas flames. Thus prevented from reaching the gas taps again, the supply teacher then had to search for the location of the emergency gas shut-off valve.

Comments from the STAO Safety Committee
Teachers are responsible for the safety of their classes instructed by a supply teacher. If the regular class teacher is absent, student laboratory activities should be avoided. The location of emergency shut-off valves (gas/electricity/and water) should be clearly labeled and known to all teachers working in a particular laboratory. The teacher should know the location and use of the fire blanket. In addition, the main gas valve should have been turned off until the class settled down, did any pre-lab instructions, had the Bunsen burners securely connected to the gas taps,ensured that all the gas taps were turned off, and all long hair tied back. Only then should the teacher have turned on the main gas valve. Experienced teachers have a responsibility to give guidance in safe laboratory practice to supply teachers.

A Purple Problem: Safe Waste Disposal from School Science Laboratories

A school custodian, collecting waste materials to be taken to the local landfill site, started a fire when he added some broken glass from a ‘Broken Glass’ container to the regular garbage which contained paper towels and some unused potassium permanganate crystals from a recent student activity. The broken glass was from a flask which had originally contained glycerol.

Comments from the STAO Safety Committee
The spontaneous combustion of glycerol (flammable) in the presence of potassium permanganate (strong oxidizing agent) should not surprise most science teachers. Accordingly, this incident emphasizes the importance of rendering hazardouschemicals safe before leaving for disposal. Whenever possible, large pieces of broken laboratory glassware should be rinsed with a surfactant solution to remove traces of the contents before they are placed in the ‘Broken Glass’ container. Under no circumstances should oxidizing agents be placed in the regular waste container. Any excess permanganates from student experiments, as they contain a heavy metal, should be stored for disposal by a licensed contractor . (See STAO publication Stay Safe! for further guidance with respect disposal of hazardous waste).