If you had a piece of equipment that measured the concentration of phosgene in the air, I could understand that you might need samples with a known concentration of phosgene to calibrate it. Snap in your 1 part per million sample and make sure your equipment reads it as 1 ppm instead of 2 ppm.
However no one has told what concentration of phosgene was in the vials found at the UN.
I just replied to you but just thought of something. Why would the be testing for phosgene? I ask this because the UN was allowing Iraq to import phosgene. Perhaps they were checking to make sure Iraq wasn’t manufacturing it themselves?