"排气通风机" can be translated as "exhaust fan" or "ventilation exhaust fan" in English.
"Exhaust fan" is a common and straightforward term used to describe a device that expels air or gases from an enclosed space.
"Ventilation exhaust fan" provides a bit more detail, indicating that the fan is specifically designed for ventilation purposes while also exhausting air.
In most contexts, "exhaust fan" would be sufficient and widely understood.