I doubt CO2 can act as a fire retardant at 0.04% concentration...

I doubt CO2 can act as a fire retardant at 0.04% concentration in the atmosphere. Are you being serious?

See theres a big fire in Texas atm

http://www.texasgopvote.com/stop-big-government/smokey-bear-caused-wildfires-texas-american-economy-next-burn-003261

Smokey the Bear - Fire Suppression has caused the Massive Wildfires in Texas

Forests need natural fires to burn so that the problems can be burned away while they are small and without causing damage to the trees. This also allows new trees to sprout and nourishes the rest of the forest. By putting out any small, natural fires, we have allowed the underbrush to build up so that when it does burn, it is devastating and the whole forest burns, trees and all.