Question

how long did the time taken for propane and carbon monoxide?

Answer 1

Combustion of propane with producing of carbon monoxide (carbon dioxide too) is instantaneous reaction. Propane can explode, but then formed carbon dioxide, in the case of controlled burning (perhaps with shortage of oxygen) usually сarbon monoxide is formed.

2C₃H₈ + 7O₂ → 6CO + 8H₂O