What chemical could be used as carbon monoxide scrubber?
Air reacting with charcoal will produce $\ce{N2},$ $\ce{CO}$ and $\ce{CO2}.$ $\ce{CO2}$ will be absorbed by calcium hydroxide or sodium hydroxide.
However, $\ce{CO}$ cannot be absorbed at ordinary temperatures and pressures. Only at $\pu{200 °C}$ and $\pu{10 atm},$ it reacts with $\ce{NaOH}$ to produce sodium formate $\ce{HCOONa}.$
Finally, $\ce{CO}$ can be oxidized into $\ce{CO2}$ by passing over hot $\ce{MnO2}$ or $\ce{Fe2O3},$ and then be absorbed by a hydroxide.