PAINT BOOTH FILTER FOR VOCS?

Q: We operate a paint booth as part of our manufacturing operation. Recently, a sales representative told us that his company’s fiberglass paint booth filters reduce the amount of volatile organic compounds (VOCs) going up the stack by up to 75%. He claims that we could use a higher- VOC coating that’s less expensive and easier to control. Could you please comment on this? B.T.

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A: It is good that you are apparently suspicious of this person’s claim. The two main purposes of any paint booth filter are to capture overspray so that it does not collect within your exhaust system, reducing its performance and creating a significant fire hazard, and to prevent paint mist from spewing from your stack and creating costly damage to your building, neighbor’s structures, and motor vehicles.

Therefore, all paint booth filters, including fiberglass units, are designed to remove particulates. It is true that this overspray contains the solvent or VOC; however, once the overspray is collected by the filter, much of the VOC will vaporize or evaporate as the rapidly moving air flows by. Yes, as more paint overspray is deposited onto the filter media, it will dramatically slow down the loss of VOC from lower layers of overspray, but again, the high-velocity air movement will cause most of the VOC to flash off the collected paint.

Furthermore, I have never seen data that paint booth filter media can capture “up to 75%” of the VOC emissions. Whenever we have permitted a paint booth, we have always assumed 0% removal efficiency even though we know a small amount may be captured.

As far as using a higher-VOC content coating, we would need to evaluate your paint booth’s permit. It will likely have a limitation on the amount of VOC content that your coating is allowed; typically this is expressed in terms of pounds of VOC per gallon, minus water as applied. In addition, you may also have a limitation on the amount of coating that can be applied in a day. Any changes in these limitations will require a permit modification and approval by your local or state air pollution control agency, and they will expect test data using USEPA-approved methods from the supplier to backup their claim. Also, assuming you can obtain modifications to your permit, do not be surprised if the agency requires stack testing of your own to verify the claims. All of this adds up to an onerous and expensive process.

In my opinion, the bottom line is that these fiberglass filters remove well below 75% of the VOCs. If you want to use them because they appear to be able to perform better than what you are now using, great, but I would not value them any further.