I've used both EtOH and propan-2-ol (IPA) for decades in ultrasonic cleaners both at room temperature and heated (quite warm to feel but not boiling hot) and ne

I've used both EtOH and propan-2-ol (IPA) for decades in ultrasonic cleaners both at room temperature and heated (quite warm to feel but not boiling hot) and never had a problem with fire.