Can ventilation system be used across floors?

It can be used, but it is not recommended. Since ventilation system requires the laying of pipes, the cross-layer use of long pipes, many elbows, large wind resistance, greater air loss, and poor effect; the use of one ventilator on multiple floors will result in large air flow, thick pipe diameter, and poor penetration. There are safety hazards when crossing the floor, the wind speed is fast and the noise is loud, and multi-layer ventilation is not allowed during later use and maintenance.

If I can open the windows for ventilation, is there no need to install a ventilation system?

Under the condition that windows can be opened, a ventilation system still needs to be installed, because the ventilation system can not only meet the oxygen content of indoor and outdoor air, but also reduce the oxygen content of indoor and outdoor air.

The impact of low outdoor noise on indoor life, and the elderly and children living in high-rise buildings also pose safety risks by opening windows for ventilation.