Ask the Expert Question-and-Answer Archive

by Ron Joseph

August, 200

Spray Booth Air Velocity (Flow Rate) to Control Dust Contamination

Q. We are spraying a conformal coating in a spraybooth. Our velocity will vary from aprox. 150 to 225 ft/min. It has been suggested this is too high. We are spraying onto small populated PC boards and we are getting foreign materials onto the board. Are there any ideal velocities that we should try and maintain?

Thank you for your e-mail. The predominant reason for having a high airflow rate or air velocity in a spray booth is to meet OSHA requirements for fire, health and safety. If your spray application is performed manually then OSHA would like to see an air velocity greater than 100ft. per minute. If the spray application is automated and no one is standing in the spray booths then OSHA's requirement drops to approximately 50ft. per minute.

For dust and dirt control it is certainly to advantage to cut the velocity as low as you can go without violating any fire, health or safety regulations.

Other than the velocity or airflow, dust and dirt enter the spray booth for a variety of reasons. If you find that by lowering the air velocity you still have not solved the problem, you might need to investigate what can be done to keep the contaminants from entering the booth. This might require you to evaluate different air intake or exhaust filters, look at booth maintenance issues, etc.

If you simply can't find a way to solve this problem you may want us to visit your facility and help you get to the bottom of this as quickly as possible.

I hope that this answer response will help you deal with the issue.

Best wishes,

Ron Joseph