Industry interest has piqued in monitoring nitrogen oxide (NOx) emissions in cogeneration facilities below two parts per million (ppm). Universities and government agencies have performed studies with inconclusive results. President Bush’s administrative issue of the Clean Air Interstate Transport Rule, calling for a 70% reduction in NOx emissions, adds particulate matter, 2.5 micron (PM2.5), and mercury to the criteria pollutant control list. Expectations are reductions will reach 70% by 2010. This new rule will affect every power plant and internal combustion boiler and incinerator, requiring emitters to better maintain their continuous emissions monitoring systems (CEMS) because the rules will cause operations near the lower limits of emission permits.