A boiler question please help gas safe people..?

wrong - anytime a fuel is burned ( natural gas, propane, wood,etc... ) this will produce carbon monoxide , or hydrocarbons. depending on the performance of the specific appliance, and or installation , this will affect the amount of carbon monoxide it can produce. a well maintained boiler is less likely to produce less carbon monoxide levels than a poorly maintained one. now if the pilot goes out , if has a 100% safety, this will shut off gas suplly to the boiler. and yes, no flame, no gas being burned, no carbon monoxide. all in all, burning a fuel will produce c.o.