Defining an Air Makeup Unit, Its Benefits, and Different Types

Every paint booth should have an air makeup unit (AMU)—but not every booth needs one. For example, non-pressurized booths do not require an AMU. However, having a booth equipped with an AMU can greatly benefit your finishing process.

What is an Air Makeup Unit?

An air makeup unit is an HVAC solution that replaces the air being brought out of a booth from exhaust fans with clean, fresh air. Its purpose is to help keep proper ventilation and air quality within a cabin for ideal spraying conditions and painter’s health. It also has heating and cooling capabilities, although cooling features are more commonly used within the aerospace industry. Some AMUs even have complete climate and humidity control.

What are the Benefits of an Air Makeup Unit?

• Having an AMU allows the booth to be pressurized so that contaminates are not drawn inside the cabin through any openings (doors, cracks, and unsealed imperfections), which help to reduce the possibility of contamination or flaws in the finish
• An AMU can bring in 100% fresh air from outside on its own, lessening the pressure on the building’s HVAC unit
• An AMU will provide more constant, consistent, and controllable temperature within a paint booth and help to improve the cabin’s air quality

What is an Air Makeup Unit’s Role in the Finishing Process?

Whether your booth is equipped with an AMU or not, it’s valuable to understand the role one plays in the finishing process. There are two ways an AMU is used: in paint mode and the curing process.

AMUs in Paint Mode

In paint mode, painting causes contaminants within a booth’s air. In fact, about half of the paint being sprayed within a booth sticks to the intended object while the rest remains airborne. For this reason, 100% fresh air is ideal for paint mode rather than recirculated air. An AMU that delivers fresh air will bring in one part of air to the booth for every one part of contaminated air that is leaving the booth.

AMUs in the Curing Process

After paint mode, cabins are heated at elevated temperatures for the curing process. During the curing process, no spraying occurs, which makes it an ideal situation for recirculation. A paint booth that is designed to support an AMU that recirculates air will use a lot less energy to achieve the necessary high temps for curing. An AMU that utilizes recirculation will deliver about 90% reused air and 10% fresh air within a booth.

Are There Different Types of Air Makeup Units?

There are generally two different types of air makeup units for refinishing: indirect and direct fire burners.

• Indirect Fire: This type of AMU uses a flame to heat up a heat exchanger (typically a pipe) to conduct heat into an AMU and into a paint booth. This process is only about 80% efficient and is known as older technology with paint booths. If this is the type of AMU your system is currently using, it may be time to consider an upgrade.
• Direct Fire: A direct fire AMU voids the need for a heat exchanger. Instead, a flame heats up a burner that comes in direct contact with the air within a paint booth. This process is incredibly more efficient, controllable, and preferable.

What Makes an Accudraft Air Makeup Unit Different?

Accudraft is a leading paint booth manufacturer with nearly 45 years in the industry—meaning we’ve had decades to transform and evolve our finishing system technology. As the industries we serve continue to grow, our equipment grows with their needs. Every air makeup unit we install is equipped with a control panel that automates pressure controls, temperatures, and modes. Painter’s no longer needs to manually switch between paint and curing modes—the CPU makes all the necessary adjustments.

To learn more about upgrading or installing an air makeup unit, contact Accudraft online.