/community-hubs/measurement-instrumentation/b/analytical-weblog/posts/optimizing-ammonia-usage-in-nox-emission-reduction-processesMono-nitrogen oxides (NO x ) including NO and NO 2 are byproducts of combustion where it occurs in the presence of nitrogen. Since the composition of the atmosphere is 78% nitrogen , this would include most places where this combustion occurs. These NOxen-USTelligent Community 13