You have just installed a new AC in your shop in Dhanmondi. By afternoon, the cool air is drifting out through the front door, flies are drifting in, and you can already imagine next month’s electricity bill. Many owners in this situation find that the answer is a properly sized air curtain above the door.

The key word is properly sized. Pick one that is too small and it barely helps. Pick one that is too big and you pay for power you do not need.

Which Air Curtain Size Matches Your Door?

The air curtain size in Bangladesh should be equal to or slightly wider than your door opening. Find your door width in the table below.

Air Curtain Size	Length	Suits Door Width Up To	Common Use
3 ft	~900 mm	~0.9 m	Pharmacy, small shop, office
4 ft	~1,200 mm	~1.2 m	Restaurant, bakery, clinic
5 ft	~1,500 mm	~1.5 m	Supermarket, showroom
6 ft	~1,800 mm	~1.8 m	Mall entrance, factory, cold room door

Not sure which one fits? View our air curtain range or send us your door size for a quick recommendation.

How Does an Air Curtain Work, and Why Does Width Matter?

An air curtain is a fan unit fixed above a doorway that blows a fast, steady sheet of air downward across the opening. If you are new to the technology, read our complete guide: What is an air curtain and how does it work

That moving air works like an invisible door. It keeps the inside air and the outside air from mixing, even while people walk in and out.

For Bangladeshi buyers, the benefits are easy to see: less cool air escaping from your AC, fewer flies and mosquitoes entering a food shop, less dust on your counters, and a more comfortable entrance for customers.

Width matters because the air sheet has to cover the whole opening. If the unit is narrower than the door, air slips through at the sides and the curtain stops doing its job. It is like trying to cover a bed with a sheet that is too short.

Step 1: How to Measure Your Door Before Choosing a Size

Take a tape measure and spend five minutes at the door. It saves a lot of trouble later.

Measure the width

Measure the full clear opening, from one side of the frame to the other. Do not measure only the door leaf or shutter. If you have a double door that stays open, measure both sides together.

Measure the height

Measure from the floor to the spot where you plan to mount the unit. Most standard air curtains work best when mounted at about 2.5 to 3 metres. Higher doors require high-speed air curtains built for 12 ft to 20 ft loading docks, so always check the maximum mounting height in the datasheet.

Note how your door is used

A pharmacy door that opens a few dozen times a day is very different from a factory gate that stays open all day with trolleys and forklifts passing. The busier the door, the stronger the unit you need.

Quick checklist before you call a supplier:

Door width and height
How long the door stays open each day
Inside versus outside temperature (for example, an AC room versus a hot street)
Power supply available (single-phase or three-phase)

CFM and Air Velocity: What Numbers Actually Matter?

What is CFM?

CFM means cubic feet per minute. It tells you how much air the fan moves in one minute. A higher CFM means more air volume.

Air velocity matters just as much

CFM alone does not tell the full story. The air stream also has to be fast enough to reach the floor and hold steady against the outside air pushing in. Think of a garden hose: a wide, gentle flow of water and a narrow, strong jet are very different, even if the total water is the same. Many standard units have an outlet speed of roughly 8 to 12 metres per second, while heavy-duty units go higher. Check the exact figure for your model.

A simple way to think about sizing

You need more airflow and speed when:

the door is wider or taller
many people or vehicles pass through
the temperature difference between inside and outside is large
wind blows directly into the opening

Our field rule of thumb (a guideline, not a guarantee): choose a unit at least as wide as your door. If the door is busy or the room is air-conditioned, move up to the next model with higher airflow rather than the lowest one.

Cold rooms and food areas

Cold storage doors and food preparation areas need stronger airflow and a sturdier build, because the temperature gap is bigger and the cost of losing cold air is higher. A light shop-grade unit is usually not enough here.

3, 4, 5 & 6 Feet Air Curtains Compared

Here is how each size is typically used in real Bangladeshi businesses.

3 Feet Air Curtain

Best for: small doors, such as a pharmacy in Mirpur, a mobile phone shop, a boutique or a small office.

Strengths: it uses little power and is easy to install. For a shop with a single narrow door, it is often all you need.

Limits: it is not right for wide entrances or doors with constant traffic. If customers regularly walk in two at a time, consider the next size up.

4 Feet Air Curtain

Best for: restaurants, bakeries, sweet shops, clinics and kitchen doors.

Strengths: this is the most common choice for standard shop doors. It covers a normal single door with a little room to spare.

Limits: it can fall short on a double door. A bakery in Uttara with a wide glass entrance may find it stretched.

5 Feet Air Curtain

Best for: supermarkets, showrooms, hospital corridors and the entrances of small garment units.

Strengths: balanced coverage for medium-traffic doors. It handles a steady flow of people better than smaller models.

Tip: if your door is between two sizes, choose the larger one. A little extra width costs far less than leaking air.

6 Feet Air Curtain

Best for: mall entrances, factories, warehouses, cold room doors and loading areas.

Strengths: the widest standard coverage and the highest airflow in this range. It suits busy openings where doors stay open for long periods.

Note: if your opening is wider than 6 feet, see the multi-unit section below.

Bangladesh-Specific Factors That Affect Air Curtain Performance

An air curtain that works well in a cool, dry country may struggle here. Keep these local conditions in mind.

Heat and humidity. In Dhaka, Chattogram, Gazipur and Narayanganj, hot and humid air puts extra load on your cooling. Humid air can also cause condensation near cold doors, so cold room installations need extra care.

Dust and pollution. City roads and industrial areas bring a lot of dust. Choose a unit with an easy-to-reach filter and a body that is simple to clean, and follow a strict schedule on maintaining an air curtain.

Power supply. Voltage often goes up and down. Make sure the unit suits your supply, such as single-phase 220V at 50Hz, and consider a stabiliser or protection device to protect the motor.

Where they are used most. Garment factories and RMG packing rooms, pharmacies, restaurants, food processing units, cold storage, hospitals and shopping malls.

Running cost. Running cost. By keeping cool air inside, an air curtain can save energy and reduce the workload on your AC. The actual saving depends on your door, your traffic and your climate, so be careful of anyone who promises an exact percentage.

Common Sizing Mistakes to Avoid

Over the years, we have seen the same errors again and again:

Choosing by price instead of door width. A cheap unit that does not cover the door is money wasted.
Looking only at CFM. Without enough air speed, the air stream breaks up before it reaches the floor.
Mounting too high or off-centre. The air sheet loses strength and leaves gaps.
Using a standard unit on a cold room door. It simply cannot keep up.
Ignoring after-sales support. If spare parts or service are hard to find, even common air curtain problems can leave you without a working unit for weeks.

What If Your Door Is Wider Than 6 Feet?

Many loading bays and large entrances are wider than a single unit. In that case, you can install two or more air curtains side by side with a small overlap, so there is no gap in the middle. For very large openings, longer industrial units or custom options may suit better.

A quick site assessment can save you from buying the wrong combination. Contact us and we will help you plan it.

How to Choose a Supplier in Bangladesh

Before you pay, check these points:

Datasheet: ask for the exact CFM, air velocity, motor power and voltage of the model.
Build quality: ask about the body material and the motor, including copper winding and bearing type.
Warranty and service: find out how long the warranty is and whether service is available in your city.
Spare parts and papers: confirm that parts are available and ask for import and compliance documents. Be careful with suppliers who claim certificates they cannot show.
Installation help: ask for installation guidance, and if possible, see a working unit at another site.

Talk to us: Seraphic Associate, Plot # 62, Road # 06, Block # A, Mirpur-12, Pallabi, Dhaka-1216 (Chattogram Office: Plot No-468, Silimpur CDA R/A Vatiery, Sitakunda). Phone / WhatsApp: +88 01750131025.

Conclusion and Next Step

Choosing the right air curtain is simple when you take it step by step. Measure your door, pick a width that covers the full opening, check both CFM and air speed, and think about your local conditions such as heat, dust and power supply.

Get it right once, and you will enjoy a cooler shop, a cleaner entrance and fewer insects, with less stress about your electricity bill.

Not sure which size to pick? Contact us today for a free air curtain sizing recommendation. Send us your door dimensions and tell us how you use the space. Our team will help you choose the right model for your needs. Call us, message us on WhatsApp, or fill out our quotation form to get started!

Frequently Asked Questions

What size air curtain do I need for a 3 ft door?

A 3 ft (about 900 mm) unit is the minimum. If the door is busy or the room is air-conditioned, a 4 ft unit gives you a safer margin and better coverage at the edges.

How much CFM is enough for a restaurant door?

It depends on door width, traffic and temperature difference. Most restaurants use a 4 ft or 5 ft unit. Check the model’s datasheet and tell your supplier how busy the door is.

Can an air curtain replace air conditioning?

No. It does not cool the room. It helps keep cool air inside, so your AC works less and your entrance stays more comfortable.

Does an air curtain work when the door is fully open with heavy traffic?

Yes, if it is the right size and strength. For busy factory or warehouse doors, choose a heavy-duty unit and make sure the width covers the full opening.

How high should an air curtain be installed?

Most standard units work best at about 2.5 to 3 metres. Always follow the maximum height given for your model, and mount it centred above the door.

3 Feet, 4 Feet, 5 Feet & 6 Feet Air Curtains: Door Width & CFM Sizing Guide in Bangladesh