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If, like me, you've ever wondered what that little puff of hot air is that touches your face as you walk through the doors of a large high street store, I'm here to break the news to you that this isn't one of life's little mysteries, it's, in fact, the effect of an air curtain. It may surprise you further to learn that air curtains can be found in a range of places you visit on a day-to-day basis such as high street stores, shopping centres, hospitals, hotels, banks, factories, warehouses, pubs and clubs, restaurants and airports.
So, what is an air curtain?
An air curtain (or air door) is created by a device which is usually (although not always) installed horizontally above an opening. The device blasts a continuous stream of air from the top to the bottom of the opening to create an air seal which prevents air or contaminants moving from one space to another. It does this without limiting the flow of traffic or blocking vision through the opening. Clever, huh?
Why use an air curtain?
The invisible barrier created by an air curtain ensures conditioned and unconditioned air never shake hands. Employee/ customer comfort within the building is increased and pollutants and pesky insects are kept at bay. Air curtains can be a necessity for businesses that are required to meet strict Health and Safety guidelines, but on a wider scale, their appeal largely comes down to the sizeable reduction in energy costs that can be made.
How does an air curtain work?
An air curtain creates an invisible barrier of high-velocity air which blocks air movement through the door. This block keeps conditioned air within the workspace and unconditioned air, pests and pollutants out. The air curtain unit is usually placed horizontally, above the entrance. It can, however, be placed to one or both sides of the opening, and in certain cases can be installed horizontally on the floor. Most air curtain devices enable air to enter the unit via an inlet grille. The air is compressed by internal fans (usually centrifugal, axial or cross-flow) and forced out through an air outlet which is directed at the opening. The fans can be direct or belt driven. Recirculating and non-recirculating air curtains are available. Recirculating air curtains collect and return the discharged air, while non-recirculating units discharge air to the environment. Recirculating air curtains are much more efficient, but non-recirculating air curtains are often chosen over their counterpart as they are usually cheaper to buy.
Things to Consider.
When selecting the size, power rating and features needed for a particular air curtain there are a number of points to consider. These include:
The dimensions of the opening (height, width and space available for installation)
The type of door being used and its location (customer entry, refrigeration, dock door etc)
The climate, exterior temperatures, prevailing winds (If you are in an area that fights strong winds, you'll need more air at a higher speed than you would need in a milder climate with no wind) and whether any drafts exist due to pressure differences at the opening
If installed correctly, an air curtain can lead to significant energy savings
A team of specifiers, consultants and installers are worth approaching if the best results are to be achieved
So, there you have it.
The 'little puff of hot air that touches your face as you walk through the doors of a large high street store' mystery: solved.