Ducting: Air Pressures Up and Down


Coming on the heels of our FX100 blog post, we’re back to talking about different options when you order ducting from Celina. And this time, it’s not just about welding!

When you are considering new ducting, the movement of the air within the duct can help you to choose exactly what style and type of ducting you’re going to be hunting for. Not so much the direction of the air, but more how that air is being moved. Much like how meteorologists talk about high pressure and low pressure fronts, the method of air movement is going to greatly impact the fabric and reinforcement choices you make.


Any time you think of moving air – natural or man-made – you’re most likely thinking of a positive pressure situation. This involves increasing pressure by adding more and more air into a defined space, like blowing up a balloon or using a desk fan. Pushing the air forward gives the air force and strength.

For positive air pressure systems, the ducting that is used doesn’t need to be able to hold its own shape. The force of the air will fill the space in the tubing, meaning that the duct itself only needs to be able to handle the base force of the air. These systems often use something called lay-flat ducting. When not in use, the ducts collapse slightly, only to billow out when air is pushed through them. Many barn ventilation systems use this method.


Negative air pressure is the lowering of pressure in order to pull or “suck” air in a certain direction. The most common version of this that you see is when people use a plastic straw to drink. By pulling the air out of their mouths, people create a low pressure zone with only the straw as an inlet to allow for pressure normalization.

When using negative air pressure to move air in tubes, the sides of the tubing must be strong enough to stand against the pressure without folding in on itself, possibly touching the other tubing wall areas and creating a seal. In these cases, Celina creates reinforced tubing in order to keep the duct wall strong.

The Right Duct for the Job

Making sure to accurately assess your duct’s use will ensure that you order the duct that will best fit your needs. Just as a shovel is more useful for planting flowers than a backhoe, knowing the job requirements can save you time and money on what might be too much of the thing you’re looking for.

If you’re having trouble finding exactly what you want, go ahead and give us a call at (888) 324-0654 to talk one on one about your ducting needs. We’re here for you!