Air coolers need cross ventilation otherwise suffocation is for sure Due to space constraints in cities, we tend to keep the air coolers inside our bed rooms itself and use it especially during summer season. And due to fear of mosquitoes entering the bed rooms , the windows are securely locked and even netted. In this circumstances when we operate the air coolers, the room wont get the cool effect. It must have the cross ventilation , otherwise in the middle of the night suffocation is for sure. Though you can switch on the fan to give some sort of air circulation to the cooler, that is not recommended.