Ive not studied this in many moons but as long as the air/fuel mixture is above stoichiometric then CO2 is produced and not CO... (at least in theory) But burning something until the flame goes out would definitely not meet that criteria
(Warren's example is safely isolated in a bag or box of course...but I can see the lightbulbs going off, for our younger membership... leave the exhaust pipe alone LMAO)
They do sell CO2 generators that burn propane (Lean burn with 10-20% excess oxygen) for greenhouse use, but they are generating supplemental levels, not trying to fumigate.
But CO might do just great too, Wal-Mart treats their meat with it to kill everything... just don't kill yourself in the process
CO2 good, CO badddddddd.... but in high enough levels both are deadly LOL