How to Select the Right Air Curtain for Your Door Width and Height

As a purchasing agent, distributor or contractor, you are not just buying a machine. You are buying a solution that must work reliably for your customer over years of daily use. Getting the size and air speed right is not optional – it determines whether the air curtain actually saves energy or becomes an expensive decoration.

Here is what you need to know.

Part 1: Door width – the non-negotiable rule

The air curtain must be at least as long as the door is wide. This is the single most important rule in air curtain selection.

If the unit is shorter than the door opening, even by a few centimeters, outside air will leak through the gaps on both sides. The air barrier is broken, and the energy savings you were counting on disappear.

The rule: Air curtain length ≥ door width

What about very wide doors?
For entrances wider than 2.5 meters, a single unit is usually not enough. The solution is multiple units installed side by side, forming a continuous barrier across the entire opening. This is common in warehouses, factory entrances and large retail stores.

What about door height?
Door height does not affect the required length. It affects air speed – which we cover in the next section.

Part 2: Door height – the speed factor

As door height increases, the air curtain must push air farther down to the floor. This requires higher air speed at the discharge nozzle, and more importantly, sufficient residual air speed at floor level.

For doors up to 3 meters high:

Standard cross-flow air curtains are usually sufficient. They provide good coverage for most commercial applications.

• Recommended type: Cross-flow air curtain

• Nozzle air speed: 8–12 m/s

• Minimum floor-level speed: 6 m/s

• Common applications: Restaurants, retail stores, offices, small shops

For doors 3 to 4 meters high:

At this height, standard cross-flow units often cannot maintain enough speed at floor level. Centrifugal air curtains are the better choice.

• Recommended type: Centrifugal air curtain

• Nozzle air speed: 13–18 m/s

• Minimum floor-level speed: 9 m/s

• Common applications: Warehouses, supermarkets, showrooms, workshops

For doors above 4 meters:

High doorways require high-performance solutions. At this height, you are looking at custom-engineered units or high-static-pressure models.

• Recommended type: Custom / high-static-pressure air curtain

• Nozzle air speed: 18–25 m/s

• Minimum floor-level speed: 12 m/s

• Common applications: Industrial plants, logistics centers, large cold storage facilities

A note on air speed decay:

The speed you see on the product spec sheet is measured at the nozzle. By the time the air reaches the floor, some speed is lost. This decay is more significant at higher mounting positions. A unit that looks powerful on paper may perform poorly in a tall doorway – which is why floor-level speed is the number that really matters.

Part 3: Other factors that affect selection

Door width and height are the starting points, but they are not the whole story.

Door usage frequency: A door that opens hundreds of times per day puts more demand on the air curtain than one that opens occasionally. For high-traffic entrances, consider higher-speed models or multiple units.

External wind pressure: If the entrance faces a windy direction, the air barrier needs extra force to resist outside wind. This is often overlooked but can make the difference between an effective installation and a failed one.

Building pressure conditions: If the building has strong exhaust systems or negative pressure, the air curtain has to work harder. In some cases, you may need a higher-spec unit than the door height alone would suggest.

Heating requirements: In cold climates, some installations require heated air curtains to maintain comfort at the entrance. This adds a separate consideration – power supply, heating elements and control systems.

Part 4: What to check before you finalize your purchase

Before you place the order, make sure you have confirmed these points with your supplier:

1. Is the unit length sufficient to cover the full door width?

2. Is the nozzle speed appropriate for the door height?

3. What is the guaranteed floor-level speed at your specific mounting height?

4. Has the supplier tested similar installations? (ask for references or case data)

5. What about voltage – does the unit match your local electrical standard?

6. Is the unit certified for your target market (CE, CB, etc.)?

A good supplier will not just provide a price. They will ask you about your installation conditions and help you avoid costly mistakes.

Summary – quick reference

Length: Air curtain length ≥ Door width. For wide openings, use multiple units.

Need help with your specific project?

Every installation is different. If you have a project in mind and want to make sure you are selecting the right unit, contact us with your door dimensions and application details. We will send you a recommendation with specifications and pricing.

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