Paint Booth Air Flow: How It Works

During spray jobs in a paint booth, the exhaust system must draw substantial quantities of air out of the shop in order to operate. These volumes must be replenished with equal volumes of air coming into the booth.

AIR MAKE-UP (AMU) is defined as…a mechanical means of replacing air that has been exhausted out of the booth.

It’s simple…. it’s all about paint booth air flow. How much air in being put into the booth and how much is being taken out. Airflow while spraying takes the over-spray away from the paint job and out of the booth.

Air in – Air out. Air in – Air out. Air in – Air out. Air in – Air out. That’s it. With the Sure-Cure Air Makeup Unit, you control the amount of air pushed into your booth. Why would you need to push air into your booth?

NEGATIVE AND POSITIVE BOOTH PRESSURE
When the exhaust fan of the booth is turned on, it creates a “negative” air pressure in the booth cabin (taking out more air than is being put in). When there is a negative air pressure, the booth will try to suck in as much air as possible, including dirt and debris from outside the booth. THINK VACUUM CLEANERS.

To counter this “negative” pressure, an Air Makeup Unit (AMU) unit is used to supply air to replace the air being exhausted. If the AMU is designed to force more air into the booth than is exhausted…the booth is said to have “positive” air pressure. In this case, the booth has more air than outside the booth and when a door is opened, dirt and debris is pushed away from the booth. THINK STANDING IN FRONT OF A FAN.

Controlling the paint booth air flow going into the booth, with relation to the air being exhausted from the booth, is critically important to maintain the proper flow of air over the item being painted and remove the over-spray effectively.

FANS TO PUSH AND PULL
The air being pushed in and pulled out are done with two types of fans. The exhaust fan that PULLS the air out of the Standard Tool’s paint booths is a tube-axial exhaust fan. It is a propeller blade type fan. Tube-axial is the best fan to be used on the exhaust of the booth because they are designed to pull the air. Aluminum blades are used because they will not spark, causing a fire, which is important when working with flammable coatings.

The fan that PUSHES the air into the booth through the Sure-Cure AMU is a blower fan, designed to force the air into the booth.

PAINT BOOTH AIR FLOW
Controlling the air flow and pressure is a delicate balance between input air and exhausted air.

When a booth is balanced, it means that the same amount of air is pushed in and pulled out (8,000 CFMs exhausted out and 8,000 CFMs pushed in through the AMU). If the painter opens the booth door, the pressure goes negative and sucks in dirt and contamination thru the open door, and all the other cracks and crevices of the booth.

When there is more air being pushed in than sucked out, you create positive pressure, so a slight amount of air is pushed out when the booth door is open. Positive pressure creates a cleaner booth.

Being able to control the airflow changes the way you paint. The Sure-Cure AMU from Standard Tools and Equipment allows you to adjust temperatures, times and booth pressure by means of the energy-saving variable frequency drive contained in the control panel. How do you know if you need makeup air?

WHAT AFFECTS PAINT BOOTH AIR FLOW?
Full Filters: Paint Booth air flow is affected when the exhaust filters become full with over-spray. As the filters fill up with over-spray, the exhaust fan must work harder to remove the air through those filters and out of the booth. With the same amount of air being pushed into the booth, but now a lower CFM being pulled through clogged air filters, the booth is over-pressurized. Over-pressurization causes dirt contamination in the booth because it severely disrupts the designed airflow and causes uncontrolled turbulence.

Adding an item inside the booth: The booth pressure is different empty than when you have something in the booth to be painted. The item in the booth takes up a certain amount of volume in the booth. You must account for this. If you continue to force the same amount of air into a booth, which now has a reduced volume, you will over-pressurize the booth (forcing too much air into the booth).

MORE ABOUT THE SURE-CURE AIR MAKEUP UNIT (AMU)

Now that you know how airflow effect the paint booth and the spray job, let me tell you a little bit more about the Sure-Cure AMU manufactured by us, a leading paint booth manufacturer… right here in Greensboro, NC. You can also read this blog when we first introduced the Sure-Cure.

We designed the Sure-Cure AMU to optimize booth efficiency, safety and operator comfort through precision controlled heat circulation. Our white powder-coated, ETL-listed units are available for both indoor and outdoor applications, either vertical or horizontal configurations, and can be retrofitted to fit any existing booth set-up.

Spray, flash, cure, and cool down … all in the paint booth. The Sure-Cure AMU has an automatic shutoff that allows you to paint it and walk away while it cures, increasing your production to at least two more projects a day (right before your lunch break and right before you go home).

HOW MANY CFM’S DO I NEED?

We can help you to determine how many CFM’s you need…. but here is a simple equation based on the model booth from the Standard Tools engineers to help you get started:

On the Cross Flow, Semi Down Draft or the Open Face Booth:

Width of Booth (in feet) X Height of Booth (in feet) X 100

On the Side Down Draft Booth:

Width of Booth (in feet) X Height of Booth (in feet) X 40

Perhaps you already have an AMU, but thinking you may need to replace it. Here’s how you know if you should.

Some of the benefits of any Air Makeup Unit:

• Reduced total energy costs.
• Enhanced finishing applications due to reduced air particulates.
• Decreased cold air infiltration.
• Increased production with an accelerated dry time

Some of the benefits of OUR Air Makeup Unit:

• ETL listed
• Available in 10K CFM or 14K CFM
• Natural gas or liquid propane
• Extra Safety Features:
  • Multi-Service Disconnect
  • Flame Failure Remote Reset
  • Loss of Burner or Flame Reset
  • Loss of Thermostat Connection
  • White Powder Coated finish for durability and professional appearance
  • User-adjustable Flash/Cure/Cool Down Times
  • Deluxe remote control panel for booth pressure, temperature, time and booth lights
  • 80-F temperature rise in 30-seconds! (100-F cure temperature rise to 160-F)
  • State-of-the-art burner and controls to allow precise controls of temperature, pressure and time
  • Meets all OSHA and NFPA Regulations
  • Quiet (65 dB) 10-hp AMU fan