You will need one PS-100 sampler for every site and every gas that your customer wants to sample.
You can sample NO, NOx, NO2 with one sampler. NOx goes on one side and NO2 on the other side and then subtract the two to get NO.
You will use another sampler for O3, as it requires two collection pads to be used at the same time, one on each side of the sampler. The two pads are analyzed together.
You will use another sampler to do NH3, using 2 pads, one on each side of the sampler. The two pads analyzed together are considered one analysis.