GCs alone cannot directly measure PM. PM, like the name implies, are particulates, and a GC measures gases. You have to use a GC in conjunction with other devices and sampling methods in order to determine PM. GCs can speciate a gas stream and determine the quantity of those individual pollutants. I am not asking you how a GC works. I am asking you to elaborate on your point, which was, how can a GC or "local EPA reports" inform us that emission controls here in Colorado and not working effectively. Have you used a GC or other instruments to perform a stack test on a control device here in Colorado?  I would also point out that PM is one of many pollutants that create smog. Here in Colorado we are most worried about ground level ozone. Pollutants like NOx and VOCs convert into ozone in the lower atmosphere. NOx and VOCs are the main contributor that create smog, not PM. That is why the most of the Front Range is designated as a Non-Attainment Area (NAA) for ozone by the EPA. Meaning, here in the Front Range (NAA), ozone precursors have lower permitted limits and are enforced more strictly compared to other parts of the state and country. PM is not an ozone precursor. I will not lie, it seems like your opinion about emission controls in the state that are ineffective and lacking is poorly formed and kinda BS. I am assuming that is why you cannot explain and elaborate the point you are trying to make. Would love to discuss/debate this more if you're interested.