The selection of an FFU involves considering various criteria such as the size of the controlled environment, the required airflow rate, the filter capacity, and the filter type. The size of the FFU should be selected based on the size of the room and the required airflow rate. The filter capacity and filter type should be selected based on the application requirements.

The advantages of using an FFU are many. It provides clean air, improves the air quality, reduces the risk of contamination, and increases the efficiency of other air filtration systems in the building. It is also easy to install and maintain and comes with a long service life. FFUs can be used in various applications, including clean rooms, laboratories, hospitals, and manufacturing facilities.

The limitations of using an FFU include the high initial cost, the need for regular maintenance, and the limited filtration capacity. FFUs may not be suitable for applications with high levels of air pollution, temperature extremes, or humidity. It is important to select an FFU that is appropriate for the application and maintain it as per the manufacturer's instructions.