Traces of vanadium in higher-temperature combustion products sort droplets of molten vanadates. These attack the passivation layers on metals and lead to superior temperature corrosion, that's a concern specifically for internal combustion engines. Molten sulfate and direct particulates also have these result. This describes why they may frequently Bogus https://broadfar.com/non-combusted-cigarettes-a-safer-alternative-or-just-a-myth/