Types of dampers

"There's a number of different types of dampers," Shinkle says. "You have air control and volume control and then you have life safety dampers — smoke and fire dampers. Life safety dampers are going to close in the event of a fire or smoke presence in the building, so it doesn't allow smoke to go into another area of the building."

Blast gate dampers, which are a type of gate valve, are often used in dust collecting systems. Bubble tight dampers, which are a form of volume control, have a 100% sealed gasket that doesn't allow any air to pass through. These are also used in laboratories. 

Dampers are either manual or automatic. The automatic "has a motor on it that sends a signal to the computer and the brains of the HVAC system will tell it when to close and how to close," he says. Manual dampers allow you to read air flow and adjust it, set it and lock it. It won't change until you re-balance the system. 

IRIS details and installation

The name IRIS comes from the iris of the eyeball, Shinkle says. When the eye dilates, it closes and opens from a center-point view, but the center of your eye never changes. The IRIS damper is a series of multiple little angled blades but as you close it, it comes together in the center. While you can leave it fully open, Shinkle says it gives you better air flow if it's 50% closed. 

"Let's say it's a 4-inch round duct, and you close it 50%, that would give you a 2-inch diameter circle in the center of the duct, not off to one side or the other. It gives you better air flow that way," Shinkle says. 

While IRIS dampers aren't 100% sealed like bubble tight dampers, they are tighter than a standard damper, Shinkle notes, which makes them ideal for laboratories and pharmaceutical settings. 

These dampers aren't the kind you're going to set and not look at for 10 years, though. Pressure and flow could be read multiple times per week, so they are mounted in the user space where maintenance or tech can walk right up to it.  

When it comes to installing an IRIS damper, Shinkle suggests following the manufacturer's instructions. 

"Along with any piece of equipment, you're trying to minimize the system effect on the air flow, but because IRIS dampers get measured or are used to measure air flow more frequently, the best recommendation is you need a minimum amount of straight duct before and after that damper in order to get an accurate reading."