Paint Booth Certification

The primary purpose of Paint Booth Certification is to gather and document possible sources of contamination within a coating operation. With this information, standards can be set and when variances occur, the situation can be quickly identified and corrected.

There are five (5) main sources of contamination that must be examined thoroughly during the booth certification process:
  • Supply Air / Intake Air
  • Object Being Painted
  • Personnel
  • Compressed Air
  • Paint

Each of these factors in themselves contain a multitude of possible contaminants. When properly addressed during a Booth Certification, the vast majority of contaminants can be eliminated.

The following methods of investigation are designed to gather information necessary to either eliminate or identify the above named factors as sources of contamination.

Visual Inspection – A Simple First Step

Visual inspection is a walk-through of painting facility from the air make-up unit to the exhaust stack making note of possible sources of contamination. When making a visual inspection, it is important to cover the five groups noted above to be considered possible sources of contamination.  Examples of what to look at in each group include:

Supply AirImproperly installed or damaged filters, changes in the atmosphere such as seasonal concentrations of pollen and agricultural activity. These all affect the volume and concentrations of contaminants which ultimately flow toward the object being painted, if not stopped by the filter system.

Object Being PaintedNaturally the appearance of the object prior to painting is the most critical observation point. Any areas which can contribute additional contaminants to the surface are noteworthy as they increase the work load necessary to remove them. Fibers, grease, and perspiration are all examples of contaminants which can occur prior to painting.

Personnel:  This is the most significant source of contamination for one basic reason – it is the hardest to control. Improper clothing, recently trimmed hair (including facial hair), and items carried into the work atmosphere such as newspapers or other printed paper items, will easily shed fibers. It is extremely important to document these variables as they will seldom remain consistent. They are, therefore, the most difficult to identify as contaminants taken from the finished product.

Compressed Air:  Visually there is little that can be attributed to this source except for moisture or purge solvents. Membrane sampling externally or inline are the most accurate means of eliminating or identifying this as a source of contamination. A particle counter survey of the individual units will be helpful in determining locations for membrane sampling.

Paint:  Once again there is little that can be accomplished by visual inspection of the paint itself, especially when conducted by untrained personnel. If paint is suspected as a source of possible contamination, it is best to leave the investigation to paint personnel and/or the vendor which supplies the paint.

Charting Air Movement Within the Booth

Three (3) things are important to the effectiveness of proper air-flow in a paint booth. They are the velocity of the air movement, the flow pattern of the air movement, and the balance of the air movement.  Explanations for each are as follow:

Air VelocityA velometer is used to measure air speed and readings are usually in feet per minute. The ideal situation requires only enough air velocity to exhaust suspended particulate (primarily overspray) and prevent it from settling on the painted surface, all the while maintaining a positive airflow in the booth. However, due to the fact many surface coat operations still utilize manually operated sprayers, parameters or minimum air velocities are dictated by environmental and safety personnel. The velocity of the air also affects the transfer efficiency of paint being sprayed. The purpose of charting air velocities is to identity any areas which have either higher or lower velocities than the preset norm. Variance in the velocities creates turbulence within the booth. Areas of turbulence can be further identified and visibly evaluated through testing with a smoke tube.

Air Flow PattersIdeally the air flow pattern in a booth should be laminar. Laminar is defined as airflow which is consistent from diffusion media (the intake air filter such as’s DS-560 product) to exhaust, flowing in a relatively straight line that envelops the object being painted in a protective air shower. Excessive turbulence within the air flow disrupts this protective air shower and subjects the object being painted to external contaminants. Patterns in a downdraft system are primarily affected by the design of the booth ceiling which delivers and disperses the air, and the location and size of the exhaust openings which controls the final direction of the air. To a certain extent, the design of the booth itself dictates the degree of turbulence or lack of laminar flow and a true evaluation should be made with a test item in the booth as would be presented for painting. This accurately simulates real conditions and provides the truest picture of proper booth balance.

Balance of Air Movement:  The best situation for air balance in a paint booth is to have slightly more supply air than air that is being exhausted. The main reason for this design is to protect the overall integrity of the booth itself. For instance, when more air is exhausted than being supplied, air will enter the booth from sources which are not filtered such as cracks in the booth walls, entry and exit areas, etc. This will then add to the potential sources of contaminants that affect paint quality. Keeping the booth slightly positive forces air out of the booth through these areas eliminating possible sources of contamination. Because of the type of booth utilized in an assembly process (which has alternating manual and automatic sprayers) it is necessary to have a slightly higher positive airflow in the manual zones adjacent to the automatic sprayers to prevent overspray from contaminating the manual zones. It is also considered normal to have an even airflow (neutral) or slightly negative air flow in to the manual zone after “tack-off and prior to flash-off”, to contain overspray which might otherwise leave the area.

The combination of these aspects of air movement within the paint booth is essential to the proper balance and integrity of airflow and any variations of the balance of the system should be considered a contributing source of contamination.

Contaminant Investigation

Particle Counter Survey:  The particle counter survey can be used as a quantitative measure of particles above a given size range (typically 5 micron and larger) in the ambient air within the paint booth, clean rooms or other areas. If particles are shown to be present, then a membrane sampling can be performed to establish the identity of these particles and their source.

Membrane Sampling and Photo Microscope:  Membranes are basically ultrafine mesh strainers designed to capture particulate in an airstream. This is done by drawing air through the screen with a vacuum pump and hose attachment. The length of sampling time can vary from 0.5 to 1.0 hour but should be consistent on all samples taken. Once the test sampling is completed the membrane is sealed with a petri dish cover and taped shut. It is then placed under a photo microscope for inspection and photograph is taken. This photograph becomes part of a reference library and all attempts should be made to have the contaminant in each photograph identified. Identification can be made easier by gathering samples of known items such as cotton, polyester or fiberglass fibers, paper fibers, overspray particulate, etc. for comparison with the contaminant.

Particle Identification:  As mentioned previously, establishing a library of known samples of possible contaminants inherent to the operation greatly reduces the amount of time spent identifying particles gathered during membrane sampling. This library should be increased whenever new contaminants are identified and the date, time, and location found should be documented as well as the suspected source. By doing this on a continuing basis, the paint facility should see a reduction in the quantity of these contaminants and paint quality should improve.

Compressed Air Investigation:  This is performed in the same manner as membrane sampling with an airline setup designed for this application.

Paint Investigation: is an expert in filters and not an expert in paint, so we would defer the examination and quality control of paint products to the paint supplier and paint manufacturer. Leading paint manufacturers offer a wide range of resources including both written materials we well as highly trained professionals to assist in the paint portion of your investigation.

Air Make-Up:  Several factors effect changes in the air make-up system, which in turn impact the quality and quantity of air being supplied to the paint booth.

The information being documented in a booth certification must be done so on a consistent basis using a standardized report form. At a minimum, any report form must be to include basic information such as name of inspector, time of inspection, area inspected, etc.

Conditions of the Supply Atmosphere:  Conditions of the air itself are important to document as they have an impact the quality of air that can be delivered down­stream to the booth. Moreover, air supply condition can impact the operating life of an air filter, so a proper understanding of air supply condition is critical if it is to be incorporated into a filter change-out / maintenance program.

  • What to Look For:  Weather conditions (i.e., atmospheric changes) fog, rain, high wind, pollen, dust concentrations, high winds, etc.  For example, high winds tend to increase velocity of the air itself and will often cause the penetration of contaminants well into the filter media, especially in systems already operating at the maximum capacity.
  • Why:  Fog and rain affect the quality of filters, especially surface loading type filters such as the pre-filters. Typically this causes a shortening of the filter’s life and a reduction in the airflow to the system through increased resistance. Pollen and high dust concentrations as well as increases in agricultural activity which parallel spring through fall, also shorten filter life because the higher dirt concentrations will load-up into the filter more quickly.
  • The time of inspection and the location are important to document. For instance, the east side of a paint facility may load faster than the west side of the paint facility due to prevailing wind direction or location of exhaust stacks which may concentrate overspray.

Filter Conditions:  Visual inspection of the filter bank itself can provide valuable information as to changes in the system.

  • What to Look For:  Improperly installed filters, or those which have become unseated from their frames, filters which visually appear past their change point. Other issues might be melted, torn, or defective products.
  • Why:  Primarily this is not to determine the quantity of the remaining service life in the filter used in the air make-up. Rather, it is to note any changes in the system on a day-to-day basis which correlates to changes in product or system quality. The information being documented must therefore be supplied on a consistent basis using a standardized report form.

Paint Booth:  Conditions which effect changes in the booth are too varied to list singularly. Yet in general overall booth balance (i.e. positive/negative air flow), the appearance of contaminants in the booth such as newspapers, rags, improperly clothed personnel, or imperfections of the mechanics of operations such as filters out of frames, holes or openings in the booth walls or ceilings, changes in the flow of the water wash, and conditions which affect the object being painted (i.e., exposed bodies, during breaks, prior to painting and visible surface imperfections) are all worthy of documentation. These are the clues that reflect subtle changes in the process which affect paint quality.

Personnel:  As previously stated, contaminants arising from this source are the hardest to control. Once standards are set; however, regarding proper clothing, material brought into the booth and proper conduct in the paint operation; variations of the standards are more easily identified and documented. The best way to combat contamination from this source is employee education. This will best be accomplished by showing a cause/effect relationship between contaminants from the finished product to their respective sources. It is best to have documentation showing the benefits to be had by greater awareness of the causes of paint damage and how easily they can be eliminated by a combined, cooperative effort.

Object Being Painted:  Careful observation of the product, prior to painting, can lend direction as to which part of the operation should be investigated further. If contaminants are present on the object prior to painting then take samples, identify, and proceed to eliminate under the same parameters as if on the finished product. Most importantly, from a time saving stand point, is to identify contaminants which are primarily found in specific parts of the process. This narrows the scope of the investigation to more manageable levels

Documenting the Evidence

As stated previously, the intent of visual inspection is to make note of changes in the process condition. These changes indicate areas where further investigation is necessary and eliminate areas that do not warrant further attention. In this respect the visual inspection is the most important diagnostic and time saving tool available.

The process of elimination used to identify contaminants can continually be refined so proper documentation of the steps taken is a valuable self-help time saver as well as a means of retracing steps in the case of an error. Presenting the evidence becomes much easier if the reference information and the elimination process has been documented. Then reference information is readily available for summarizing your reports.

Once a determination has been made that a contaminant source relates to some aspect of the personnel present in the process, a cause and effect relationship needs to be established.

It will be necessary to document improvements in the finished product after eliminating the contaminant. The before and after comparison then becomes a tool for gauging the effectiveness of these system improvements.

The best way to identify the contaminants from this source is an extensive photo library which can be used as a cross reference for known contaminants versus those taken for identification. By doing this cross reference identification, a foundation for the cause and effect relationship is established and employee awareness can be improved.

Because of the inconsistency inherent to this contaminant factor, identifying the contaminant will be easier than pinpointing its specific source. This is due largely because each individual present in the operation is a constantly changing variable.

Employee awareness and cooperation is necessary to begin eliminating this source as a contaminant factor.

Reporting the Information

How to Report:  As stated previously, the use of a standardized report form will provide the most consistent and accurate flow of information. These reports will, from time to time, need to be modified to reflect changes in equipment and processes. In the attached addendums there are examples of possible forms to be used as guidelines to compiling and reporting information gathered during investigations.

Preparations must be made for maintaining appropriate files to store this information for cross reference at future times. This is especially critical during the early stages of the program to help establish operating norms.

Who to Report to:  In general, information gathered by the investigative team should be consolidated and given to their immediate supervisor.

The exceptions to this are situations of a critical or emergency nature where it may be necessary to report immediately to the Process Engineer and/or the Area Manager.

In the majority of cases the investigative team will compile this information with the assistance of their immediate supervisor. The supervisor will be responsible for reporting to his or her supervisor and will instruct the investigative team to report their conclusions to other parts of the organization. Based on their findings appropriate courses of action can be discussed and necessary actions taken.