Will a dehumidifier reduce mold risk caused by a gas fan heater?

I thought it would. But today a K's denki ojisan told me the opposite, that mold would grow more if I use a dehumidifier 除湿機 together with a gas fan heater. It made no sense to me. My layman logic assumed a gas fan heater will produce moisture and a dehumidifier will kill it, all together reducing the risk of that mold called 'kabi' here. I hate it. Our new apartment is renovated and I don't want any mold on our snow white wallpapers. Has anybody used a gas fan heater together with a dehumidifier? Did it work for reducing the risk of mold or what?

by hlbm