We use the VentMaster which is a rebranded Husky 576xp w/ 20 inch hard nose .404 bar, raptor or bullet chain, and a case/ muffler guard. We have 10 trucks and 1 heavy rescue, every unit carries a vent chainsaw, 3 cut-off saws, and one "wood" chainsaw. The vent masters get pretty beat up. We do a lot of vertical vent cuts and use them to cut gable ends on Garden apartments. We usually take the VentMaster and one cutoff saw to the roof (based on building construction). Be prepared for a lot of maintenance for the saws FD personnel are hard on equipment and saws tend to see the worst environments. An air filter usually only lasts one good fire, we carry multiple spares on the trucks and extra chains. Not sure if your aware of the difference between the Stihl Duro carbide chain and the stihl duro rescue chain ( the same as the bullet and raptor chain in theory). The rescue chains use a larger Brazed piece of carbide and dual cutters to support the carbide on both sides, compared to the stihl duro carbide that you see in most saw shops.
Yes you can cut light gauge metal, like garage doors, with the rescue chains BUT it will chip the cutters and a&e the saw chain out of service, price of doing business with these saws. You can end up having $1,000 in just chains for one saw. You also have to find someone willing to sharpen or repair the chains, they require diamond wheels. We actually ship our chains across the country from Florida to California to have them sharpened or repaired.
I recommend an in service saw class and maintenance class, the amount if poor maintenance and backyard saw "truth" that you will see and hear is astounding.
