There is an article dedicated to this at BPL (http://www.backpackinglight.com/cgi-bin/backpackinglight/stoves_tents_carbon_monoxide_pt_4.html) but you need to subscribe to read it.
According to that the lowest emission was the Ion stove (114 co ppm), the highest the Triad XE at 313.
The White Box was at 160 and the 10-20 (Caldera cone) at 193. The Trangia was at 285.

Franco