While I have never used ultrasound in glove boxes, it is standard 
practice to use electrical equipment (stirplates, heat guns, static 
spark discharge devices, rotary evaporators, etc.) in inert 
atmosphere glove boxes even in the (heavy) presence of flammable 
materials.   I have done it thousands of times, and I know dozens of 
professors who have done (and continue to do) so similarly and have 
never heard of a single problem/incident.

O2 levels in inert atmosphere boxes are always kept in the ppm range, 
so it shouldn't be a concern unless someone was being mind-bendingly 
incompetent.   Standard fire or explosion is physically impossible at 
that level of oxygen.

Explosions can, of course, occur within glove boxes from other 
processes such as the mixing of incompatible materials, synthesis of 
unstable compounds (and/or shock-sensitive) materials etc.   My 
firsthand experience with explosions within glove boxes are 1. A 
flask implosion on a rotary evaporator, presumably from a star crack 
and 2. Detonation of a substance which turned out to be 
shock-sensitive.  In the latter case, the Lexan bulged out and crazed 
a bit, but there was no injury to the person who was holding the 
material in his hands when it went off and there was no fire (of 
course, as there was no oxygen).

Note that it is also standard practice to purge the box atmosphere 
after using volatile materials.  Be sure that the purge vent is 
routed to a fume hood or other suitable non-sparking ventilation 
source.

Rob Toreki

>One of our scientists has asked for guidance in the use of inert (N2)
>atmosphere glove boxes for processes utilizing flammable liquids and
>electrical appliances. Details of the process of concern follow:
>*	Dispersed (in xylenes) silicon nanoparticles are to be further
>dispersed using a SS ultrasonic wand (20 kHz)
>*	Process to be performed in a N2 atmosphere glove box
>*	Monitored O2 levels will not exceed 10ppm in the box
>*	All power to the glove box (including the wand) is cut upon
>exceeding 10ppm O2 concentration in the box
>*	The lab bldg is provided with a fire sprinkler system as well as
>CO2 extinguishers within 10 ft
>
>Questions:
>*	Is there a (any) concern regarding the use of a wand-type
>ultrasonic to agitate a flammable solvent in an inert atmosphere?
>*	Should this level of O2 (flammability perspective?
>*	Under this scenario, at what O2 levels should fire reasonably be
>a concern?
>
>I appreciate any and all feedback on this topic.
>Regards,
>
>I Jay Saldivar
>Sr Safety Administrator
>Sharp Microelectronics of the Americas
>NW Pacific Rim Blvd
>Camas, WA  98607
>
>360/834-8734 (o)
>360/772-4502 (c)
>saldivarj**At_Symbol_Here**sharpsec.com

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