When looking for a root word you want to locate the part of the word that doesn't include prefixes or suffixes. The root of exventare is 'vent', which is seen in the word ventilator.
The definition also aligns with the root word (ventus, meaning wind), because a ventilator is a type of fan that allows air to exit a room. In medicine, it is also a device that helps a person breathe--allowing air to enter and exit their bodies.
