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I use a sonicator at work in a cleaning process. It involves sonicating acetone, NMP, and IPA. We would like to move forward with other flammables as well. We currently do the work in a hood, but no other precautions are taken. OSHA has no guidance. What is your experience with this issue?

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    $\begingroup$ Done this many times without problem $\endgroup$ – Waylander Feb 11 at 20:20
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In general it should be relatively safe considering you take all the precautions required when working with volatile flammable liquids. Specifically for sonication I can think of two safety aspects:

  1. Sonification promotes formation of the aerosol/fog consisting of the atmospheric gases and solvent vapors. Depending on its composition, it might or might not be fire hazardous or even explosive. That's why keeping an ultrasonic setup in a ventilated area — a fume hood, ideally — is a good idea. Keep the power supply and all controller circuits outside, if possible, in order to prevent spark vapors ignition.

  2. Be careful when sonicating heterogeneous solutions. Some materials would absorb the ultrasonic energy and this can result in local overheating. To prevent this, use mechanical stirring.

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    $\begingroup$ +1 especially for keeping an eye on temperature control since -- due to the cavitaion noise it is easy to close the hood, "forget it" and return surprised how warm the water bath got in the meantime (e.g., running an us-assisted acetalization with aceton). $\endgroup$ – Buttonwood Feb 11 at 21:06
  • $\begingroup$ A very good point. I've run Zn/NH4Cl reductions in MeOH under ultrasound and after an hour needed to change the water because it had got significantly hot. $\endgroup$ – Waylander Feb 11 at 22:11

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