The definition of a commercial ERV (Energy Recovery Ventilator) is a device that helps to improve the air quality of a building by exchanging stale air with fresh air from outside. It works by taking in the stale air from inside the building, cooling or heating it, and then pushing it back into the building. At the same time, it takes in fresh air from outside, heats or cools it, and then pushes it into the building. This helps to maintain a healthy air quality in the building, as well as reducing energy costs. Commercial ERVs are typically used in larger buildings, such as office buildings, hospitals, and schools, as they require a larger system to handle the increased air flow. They are also used in industrial settings, such as factories, where they help to keep the air clean and safe for workers.