Air curtain controllers regulate the air velocity of the air curtain. Air curtains are often used to prevent air or contaminants from moving from one room to another. In winter, it can create a thermal barrier to keep warm air inside the building - for example, when the warehouse door opens to load a truck. In case of manual air curtain control, the air velocity can be adjusted via a switch or potentiometer. This can be done locally or remotely. For automatic air curtain control, an HVAC sensor is connected to the AC fan speed controller or EC fan of the air curtain.