juker
Soda Blasting wouldnt work because its a " line of site " type of operration youd have to be able to see what your blasting its not like being able to send a spinner down the duct
I notice you say "hoods" do you mean the canopy and plenum when you refer to "hoods" or do you mean the whole system as in fan, duct, plenum and hood? I think just some old fashion scraping with a good sharp scraper and elbow grease would do it, if the carbon is in the duct work install some doors and some more scrapping, If you scrape all the carbon off the first time I wouldnt think youd have to do it the next time if the job was done right and the cleaning sched. is right , I notice you say "you clean them regularly" whats "regularly"? every 8-12 weeks? If you clean them and by the next service date there charred again up the cleaning freq. We do a lot of steak houses that cook over wood fired grill pits and we do some every Two weeks and some every four weeks. its not always what you have, but how you use it
Richard