405nm is in the UVA band. You can find exposure limits for UVA easily (it's used for suntanning and 'blacklight' lamps - the ones used in disco lighting). You could use a regular blacklight lamp and skip the tests because those are approved for indirect lighting at least. Peter -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu