Mechanical system and Ventilation system

Mechanical system noun - A system of elements that interact on mechanical principles.

Ventilation system and mechanical system are semantically related. In some cases you can replace phrase "Ventilation system" with "Mechanical system", this phrases are similar.

Ventilation system noun - A mechanical system in a building that provides fresh air.

Mechanical system and ventilation system are semantically related. You can use "Mechanical system" instead a noun phrase "Ventilation system".