A couple of undergraduate students in Mechanical Engineering want to make a Einstein-like refrigeration unit for their senior project.
(http://www.guardian.co.uk/science/2008/sep/21/scienceofclimatechange.climatechange -- it’s also on Wikipedia.  These aren't the exact models, but it is the concept.)
They are seeking safety guidance from EHS.  They want to use isobutene (0.337 kg), ammonia (0.21kg), and water (0.636kg) in the table-top system.  They plan on building it in a chemical fume hood and they hope to eventually make it portable for demos. 
The pressure will be no greater than 50psi and the unit will be built with stainless steel and welded together by a professional welder.

Questions:
1.  Has anyone had such a unit built and what safety requirements were in place:

2.  PPE -- Should we require a Nomex lab coat?  Face shield, in addition to impact resistant goggles?
3.  What's the best way to address the potential flammability issues?  In a fume hood with the sash as low as possible.  Any monitoring or sensing?

Any input that you may have will be helpful.  I also don't want to miss any important questions that I should be asking them.

Thanks to you all in advance!

Marjorie Markopoulos, M.S.

Biological and Chemical Safety Officer

Department of Environmental Health & Safety

Wright State University

3640 Colonel Glenn Hwy.

047 Biological Sciences II

Dayton, OH  45435

Office:  937-775-2797

Cell:  937-239-7936

marjorie.markopoulos**At_Symbol_Here**wright.edu