FAQs

What is the relationship between paint booth air velocity and paint gun pressure?

What is the relationship between paint booth air velocity and paint gun pressure?

Is there a rule of thumb or formula to determine or calculate spray booth air supply velocity w.r.t. the amount of paint required for a particular part? Paint booth air velocity and paint gun pressure are independent of each other. Paint companies want 80 to […]

Which airflow style creates the cleanest paint job?

Which airflow style creates the cleanest paint job?

Pressurized downdraft airflow provides the cleanest paint jobs in a spray booth. Pressurized paint booths keep the cabin of the spray booth at a positive pressure, so no outside contaminants can make their way through a leaky seam or seal for dirt or dust to […]

If you are painting something large, like a truck, would overspray on the trail side of the air cause problems?

If you are painting something large, like a truck, would overspray on the trail side of the air cause problems?

Potentially, yes. A lot of large equipment businesses have switched to downdraft booths for that reason, as long as the product does not require the bottom to be painted.

If you are having problems with overspray trailing off and ending up at the backside of what you are painting, contact your paint company. Sometimes they will adjust hardeners and reducers to make the paint more wet, so it actually melts in when it hits the back panels. When you reach that section with your spray gun, it will flow the paint directly over the top of that.

You should also be conscious of where you are spraying. With a crossdraft or semi-downdraft airflow, start at the front of the paint booth and work your way toward the back. If you work the opposite way, as you get to the front of the spray booth, overspray will drift over the top of the paint you just applied. If any dust or dirt enters the spray environment, it will also get caught in the paint.

What is the best way to control relative humidity in paint applications?

What is the best way to control relative humidity in paint applications?

This depends on what you are spraying and the surface you are spraying on. There are a lot of waterborne paints that require low humidity to dry out the air and help them dry faster. It is best to reference the technical data sheet of […]

Should you use tact-based coat before using clear?

Should you use tact-based coat before using clear?

Yes, for the most part. However, there are always exceptions. For instance, if you spray a fine mist as your last coat of base (seen with some waterborne paints in automotive refinish), tacking it could remove it. If you are spraying basecoat, you want to […]

What is the worst contamination/dirt scenario you have seen in a paint booth?

What is the worst contamination/dirt scenario you have seen in a paint booth?

We have seen a full range of paint booth contamination scenarios. Typically, when businesses put in new equipment, they also change a lot of other things in the shop, which can result in contamination in the spray booth.

For example, one shop we worked with started getting little blue fibers in their paint all of a sudden. They talked to their paint reps and jobbers, but they still could not figure it out. What they learned was that a change they made in their shop processes resulted in this booth contamination. When they changed their paint booths, they also changed their uniforms — to a new blue color. They discovered that these new shirts were pilling and the fibers were landing in the paint jobs. A quick remedy would have been to wear paint suits, which help protect the painter and prevent contamination. Following a basic safety practice could have saved them months of rework.

Another time, a manufacturer set up all of their mixing operations inside their paint booths on the intake side. Multiple tables, paint cans, guns, towels, rags, hoses and a variety of other items had been in their spray booth for a long period of time. Since the intake air passed over the top of all of it, everything they were painting was covered in dirt and contaminants from their mixing operations inside the booth.

Other scenarios that could be remedied with common safety practices include not changing filters regularly, and sometimes even from storing and eating food in a paint booth, causing food particles to show up in the paint.

Outside of that, the worst damage can be seen from silicone entering the paint environment. This can be caused by cleaners used in other parts of a shop, especially if there is a detail department. Ideally, you should always use silicone-free cleaners. Some new cleaners will claim to be silicone-free, yet they include an additive that reacts the same way as silicone. Spraying just a small amount of that into a shop will cause fisheyes in the finish. To prevent this problem, keep your detail areas completely separate from the paint shop — in a different building or walled off.

How often do you see external factors affect the paint job?

How often do you see external factors affect the paint job?

We see it quite often in the industrial realm, since many people use open front paint spray booths, which pull air from the shop environment, or even from outside. This can often introduce contaminants into the paint booth. There are a lot of things to […]

What is your recommendation for filters in an open-front spray booth when using CARC paint?

What is your recommendation for filters in an open-front spray booth when using CARC paint?

We recommend GFS Wave® exhaust paint booth filters from Global Finishing Solutions®. They are polyester filters with a large surface volume. The ridges or “waves” on the filter media capture and retain overspray, acting as a 3D loading system. Flat exhaust filters get clogged very […]

Is there specific guidance where a particular zone starts, or is the whole booth regarded as one zone?

Is there specific guidance where a particular zone starts, or is the whole booth regarded as one zone?

We are a joinery company and have a booth with a 3.0m wide dry back extract for lacquer finishing. Our insurance company has raised concerns regarding the zoning within the room.

In both the US and Europe the interior volume of a spray booth is considered to be a single area classification.

United States

In the US, NFPA 33 Standard for Spray Application Using Flammable or Combustible Materials 2011 Edition, provides guidance on the electrical area classifications in and around a spray booth. It states that the interior of a spray booth or spray room is considered Class I, Division 1. The external volume within 915 mm (3 feet) of openings, including closed doors, is Class I, Division 2. Chapter 6 provides diagrams for the various styles of booths as well as for open spraying.

Europe

In Europe, the standard is EN 12215 Coating plants – Spray booths for application of organic liquid coating materials – Safety requirements. In the 2009 Edition, the Zone classification is based upon the concentration of flammables. It states that if you are between 25% and 50% of the LEL, then the interior of the spray booth is Zone 1. If you are less than 25% of the LEL, then the interior is Zone 2. In all cases, the external volume within 1 m of permanent openings is classified Zone 2. This information is taken from Section 5.7.2.3 and Figures A.1 and A.2.

In addition to following industry codes and standards, we recommend that you consult with the local authority to ensure you are in compliance with local codes and standards.

What are the regulations regarding intrinsically safe electronic devices inside a paint booth?

What are the regulations regarding intrinsically safe electronic devices inside a paint booth?

If allowed, what type of certification and enclosure does a communications device require to go into a paint booth? National Fire Protection Association The interior of a paint spray booth or room must meet the requirements for a Class 1 Division 1 area as defined […]