Ductwork Mold Eliminator Options

Please help! I'm getting new ductwork put in and want to take advantage of the opportunity to start fresh and mold free… any suggestions on devices that actually work while not being hazardous to our health by producing ozone? We were originally going to get the halo zero, but saw horrible reviews on it saying it doesn't really work (feel free to correct me if i'm wrong). Please help! They come here in a little over a week to do the work! I have asthma and we have mold in the current ductwork so I really need something to keep me healthy at home. Thanks in advance!

(i realized we are spending thousands but not replacing the furnace or other hvac components that are full of mold too… so need to make sure the ductwork stays clean/mold free – all suggestions are more than welcome)!