Back up to Index Judge the acceptability of using the substance or technique, If there is very little chance of an accident happening and the consequences are not very serious there is no reason to worry. If, however, the accident is almost certain to happen and the consequences are very serious we MUST NOT accept the risks. What we do is to multiply the the chances by the seriousness. So if you are using a three point scale for both chance and seriousness you will end up with a number between 1 and 9. Now we know what the risks are.
Every hazard has an associated risk.
We have quantified the risk on a 1 to 9 scale. Do this for every hazard you can think of and use the schema to record it. Above this level I think you should seriously consider changing your procedures or not doing the work. The accident is certain to happen and you will not live to do another experiment. You must modify the procedure or use different substances to reduce the risks if they are significant or reject the whole experiment.