If you need paint spray booth testing assistance as discussed in this article, call us at 1-800-344-4414 or email us at firstname.lastname@example.org for details and a free estimate.
Written By: Robert E. Sheriff, MS, CIH, CSP, President
January 1, 2019
There are two basic approaches to testing a paint spray booth for proper operation:
- Testing air flow.
- Testing worker exposure to spray paint emissions.
In most cases, it is necessary to test both air flow AND worker exposure to the paint components.
- Testing Air Flow – Face Velocity
The amount of air flowing into the paint booth must be sufficient to overcome the over spray from the spray gun.
The first set of tests should be to test the FACE VELOCITY of the booth.
That is: using a velometer, thermo anemometer, vane anemometer, or other airflow measuring device test the airflow at the face of the spray booth. It is best to set up an imaginary grid across the booth’s face.
(Small Booth-At Least 6 Grids)
(Large Booth-9 or More Grids)
Take airflow measurements at the center of each grid—then average the airflow from all grids.
Average: 100 units feet per minute (fpm) = “V” (Velocity).
In most cases, 100 fpm is sufficient to capture the paint emissions—as long as the spray is directed inward toward the exhaust (rear) of the booth.
The total exhaust volume can be calculated using the formula:
Q = AV where A is the area of the booth (length x width) and V is the measured air velocity in feet per minute-(fpm) where Q = air volume in cubic feet per minute (cfm). QCFM = VFPM X Aft2.
- Testing Air Flow – Capture Velocity
However: The real measurement of the air movement that is effective at containing the paint spray is the CAPTURE VELOCITY: that is the airflow at the point where the paint spray is actually emitted or at the operator’s breathing zone. Ideally that is at the booth face—the FACE VELOCITY.
Sometimes the spray emissions point is outside the booth thus, the CAPTURE VELOCITY must be taken from that point.
If 100 fpm is what is desired to control the spray paint emissions, then that is the airflow needed as the CAPTURE VELOCITY whether outside the booth or inside the booth.
As expected, if the capture point is outside the booth, then consideration must be given to the distance outside the booth where the appropriate capture velocity is needed. That changes the formula from:
Q = AV to:
Q = V (5 X 2 + A) where X = distance from booth face to capture point-(in ft).
NOTE: The further the capture point is from the booth’s face, the greater the air volume to capture the paint spray emissions.
- Testing Worker Exposure For Effective Booth Air Flow
The real measurement to establish the effectiveness of the airflow is whether the paint spray operator is protected from the paint spray solvents and particulates.
If the paint spray operators exposure is acceptable, (OSHA Compliant or otherwise within acceptable exposure limits), then the spray booth is performing as needed and intended—regardless of the airflow!! Thus, the true test of adequate airflow is monitoring the worker using proper industrial hygiene monitoring methods.
If the worker sampling/testing indicates an overexposure, then the airflow measurements are important by defining the current airflow so that it can be increased appropriately and thus result in proper capture velocity—and worker protection.
Too often decisions are made on adequacy of air flow/air volume without monitoring the worker’s exposure to the paint emissions.
The ideal situation is to monitor the worker for the contents of the paint (consult the Safety Data Sheets-SDS) and measure the Capture Velocity/Face Velocity and Exhaust Volume (Q=AV) of the booth at the same time.
We have the ability to monitor workers’ exposures and measure the ventilation systems. If you need assistance, contact us at email@example.com or 1-800-344-4414.
Industrial Ventilation Manual, Volume I-Design, American Conference of Governmental Industrial Hygienists (ACGIH), 29th Edition, 2016.
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