How Does an Air Curtain Generate a High-Speed Airflow Barrier?

2026-09-10

1. What Is the Physical Principle Behind an Airflow Barrier?

An Air Curtain works by creating a continuous stream of high-velocity air across the full width and height of a doorway. This air stream acts as a virtual door that separates the indoor and outdoor environments. The barrier is effective because the momentum of the air stream resists the pressure difference between the two spaces. The pressure difference can be caused by wind, stack effect (the tendency of warm air to rise), or mechanical ventilation. The key parameter is the air velocity at the discharge nozzle. If the velocity is too low, the air stream will be deflected by the pressure difference and the barrier will fail. If the velocity is too high, the air stream will generate turbulence and noise, and it may actually increase the infiltration of outdoor air by entrainment.

The momentum equation: The barrier strength is proportional to the mass flow rate multiplied by the velocity. For a given door width, the mass flow rate is determined by the nozzle discharge area and the air density. The velocity is determined by the fan speed and the nozzle design. The optimal velocity is typically 10 to 15 m/s for a door height of 2 meters, and 15 to 20 m/s for a door height of 3 meters.

In our factory, we design Air Curtain units with a precise nozzle geometry that produces a uniform velocity profile across the full discharge width. A non-uniform profile creates weak spots where the barrier can be breached. We use computational fluid dynamics to optimize the nozzle shape and the fan impeller design.

2. What Are the Key Components That Determine Air Curtain Performance?

An Air Curtain consists of four main components: the fan, the nozzle, the housing, and the control system. The fan generates the airflow. We use centrifugal fans with forward-curved impellers for low-noise applications and backward-curved impellers for high-pressure applications. The nozzle directs the airflow into a concentrated stream. The housing contains the fan and the nozzle, and it determines the mounting configuration. The control system manages the fan speed, the heat output (for heated models), and the door activation. The table below shows the typical specifications for our standard Air Curtain models.

Model	Door width (mm)	Max door height (mm)	Air velocity (m/s)	Air volume (m³/h)	Power (W)	Noise level (dB)
EB-1000	900 – 1000	2000	12 – 14	1100	120	52
EB-1500	1400 – 1500	2500	13 – 15	1800	180	55
EB-2000	1900 – 2000	3000	15 – 18	2600	250	58
EB-2500	2400 – 2500	3500	17 – 20	3400	320	61

The air velocity at the nozzle is the most important specification. A velocity below 10 m/s will not create an effective barrier for a door height of 2 meters. A velocity above 20 m/s will create excessive noise and turbulence. Our factory tests every Air Curtain model at the specified door height to verify the barrier effectiveness.

3. How Does Installation Geometry Affect Barrier Effectiveness?

The installation geometry is as important as the Air Curtain itself. The unit must be mounted horizontally above the door, with the discharge nozzle facing downward. The distance between the nozzle and the door header should be minimized to prevent air from escaping around the sides. The nozzle angle should be slightly toward the outside (5 to 10 degrees) to counteract wind pressure. If the unit is mounted too high above the door, the air stream will lose velocity before it reaches the floor, and the barrier will be incomplete. The table below shows the recommended installation parameters for different door heights.

Door height (mm)	Recommended mounting height above door (mm)	Recommended nozzle angle (°)	Minimum air velocity at floor (m/s)	Required air volume (m³/h per meter width)
2000	0 – 100	5 – 10	2.0	1100
2500	0 – 100	5 – 10	2.5	1400
3000	0 – 150	10 – 15	3.0	1700
3500	0 – 150	10 – 15	3.5	2000

The minimum air velocity at the floor is the velocity required to maintain a continuous barrier at the bottom of the door. If the velocity drops below this value, the barrier will be breached by foot traffic or wind. In our factory, we recommend that the Air Curtain be mounted as close to the door header as possible. We also provide adjustable mounting brackets that allow the nozzle angle to be fine-tuned on site.

4. What Are the Common Mistakes That Reduce Air Curtain Effectiveness?

There are four common mistakes that reduce the effectiveness of an Air Curtain. The first is undersizing the unit for the door width. An Air Curtain that is too narrow will leave gaps at the sides of the door. The second is mounting the unit too high above the door. The air stream will lose momentum before it reaches the floor. The third is failing to seal the sides of the doorway. If there are gaps between the Air Curtain and the door frame, air will escape around the ends of the unit. The fourth is operating the unit at too low a speed. Some facility managers reduce the fan speed to save energy or reduce noise, but this compromises the barrier. In our factory, we recommend that the Air Curtain be operated at the designed speed whenever the door is open. The energy consumption of the Air Curtain is a fraction of the energy wasted by an open door without a barrier.

Frequently Asked Questions About Air Curtain Performance and Selection

Question 1: What air velocity do I need for a door that is 3 meters high?

Answer: For a door height of 3 meters, the recommended air velocity at the nozzle is 15 to 18 m/s. The velocity must be sufficient to maintain a minimum of 3.0 m/s at the floor level. If the velocity is too low, the air stream will be deflected by wind or stack effect, and the barrier will fail. If the velocity is too high, the air stream will create turbulence and noise. In our factory, we recommend using an Air Curtain with an adjustable fan speed so that the velocity can be optimized for the specific site conditions. We also provide a velocity measurement service to verify the installation.

Question 2: Can an Air Curtain be used on a door that is exposed to strong wind?

Answer: Yes, but the Air Curtain must be sized to overcome the wind pressure. The wind pressure on a door is proportional to the square of the wind speed. A wind speed of 10 m/s creates a pressure of approximately 60 Pa. The Air Curtain must generate enough momentum to resist this pressure. For doors exposed to strong wind, we recommend increasing the air velocity by 20 to 30 percent above the standard value for the door height. We also recommend mounting the unit with the nozzle angled slightly toward the outside (10 to 15 degrees) to deflect the wind. In our factory, we offer high-velocity models specifically designed for wind-exposed entrances.

Question 3: How much energy does an Air Curtain consume compared to the energy saved by keeping the door open?

Answer: An Air Curtain consumes 120 to 320 watts, depending on the model. The energy saved by preventing the air exchange through an open door is typically 5 to 15 kilowatts of heating or cooling capacity. In a typical commercial building, the Air Curtain pays for itself in energy savings within 6 to 18 months. The exact payback depends on the climate, the door usage frequency, and the cost of energy. In our factory, we provide a simple payback calculator that uses the local climate data and the door usage pattern to estimate the annual energy saving. We also offer heated Air Curtain models that provide additional comfort for customers and employees.

Summary for Facility Managers

An Air Curtain generates a high-speed airflow barrier by discharging a uniform stream of air across the full width of a doorway. The effectiveness of the barrier depends on the air velocity, the nozzle design, the mounting geometry, and the installation quality. When these factors are properly addressed, the Air Curtain reduces the infiltration of outdoor air, maintains indoor comfort, and reduces energy consumption. When they are neglected, the Air Curtain becomes an ineffective appliance that wastes energy and provides no benefit.

EVERBESTEN manufactures Air Curtain units for commercial and industrial applications. Our units are tested for air velocity, uniformity, and noise level. We provide full installation guidelines and site-specific recommendations for each project.

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