Matt Mosley >Actually I know a little about them. Spark and Arc sources were >traditionally used for atomic analysis of solid metal samples, but suffer >from sampling problems and matix inconsistency. The resulting spectra >can Matt, thank you for the insight. I am just trying to make a yes/no decision on the presence of a hefty (5% or more) percentage of gas in air. I know that the broadened spectrum can be very hard to interpret but I do not need to determine % and each component. It would be nice to be able to tell which gas it is though. Peter -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.