The purity of hydrogen fuel is important in engine testing at SSC. The hydrogen may become contaminated with nitrogen, argon, or oxygen. The hydrogen from the fuel tanks or feed lines is analyzed beforehand. Therefore, there is a need for a non-intrusive, on-line, near real-time monitor for H2. The analytical technique should measure various impurities (molecular and atomic) simultaneously and be easy to implement in the field. The objective of this proposed research is to develop an analytical technique based on Laser Induced Breakdown Spectroscopy (LIBS) to measure simultaneously the concentrations of nitrogen (N2), argon (Ar) and oxygen (O2) contaminants in hydrogen (H2) gas storage tanks and supply lines. Advanced sensors for monitoring multiple species in H2 feed-lines and storage tanks will be useful before engine testing and will increase understanding of engine performance. Phase I will provide necessary information to build an improved prototype in Phase II, with better sensitivity and ease of implementation at NASA/SSC. In Phase II, a prototype LIBS system will be developed to measure impurities in H2 fuel at different places in the H2 feed line. This system will be delivered to NASA/SSC at the end of Phase II.