That article is not factually correct: phosgene can be detected from 4 particles per million according to Wikipedia.
Something else:
Low (<0.5 ppm): Odor recognition occurs around 0.5 ppm, but is not sufficient to protect. May be health
problems.
Medium (0.5 - 5 ppm): Exposure to 1 ppm causes little irritation, but may lead to fluid in the lungs after some
period of time. 3 ppm causes immediate throat irritation. 4 ppm causes irritation of the eyes, and 5 ppm causes a
cough.
High (30 - 300 ppm): Three phases occur. first phase includes eye and throat pain, with chest tightness and
shortness of breath. Some heart effects occur in the first phase. The second phase is without symptoms. In the
third phase, fluid collects in the lungs, sometimes leading to death. Exposure to 50 ppm may be immediately fatal.
http://dec.alaska.gov/air/anpms/toxics/noncarc/phosgene10.pdf
Not saying that the guys made everything up, but he indeed seems to be exagerating. And even then, everyone knows you shouldn't heat aggresive chemicals in any way.