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Optimal Spray Booth Air Velocity


OSHA Standard: 


The spraying operations except electrostatic spraying operations shall be so designed, installed and maintained that the average air velocity over the open face of the booth (or booth cross section during spraying operations) shall be not less than 100 linear feet per minute. Electrostatic spraying operations may be conducted with an air velocity over the open face of the booth of not less than 60 linear feet per minute, or more, depending on the volume of the finishing material being applied and its flammability and explosion characteristics. Visible gauges or audible alarm or pressure activated devices shall be installed to indicate or insure that the required air velocity is maintained. Filter rolls shall be inspected to insure proper replacement of filter media. 

Chemco Manufacturing Notes:

  • In most applications, the higher the air velocity, the lower the transfer efficiency.
  • If the air velocity is too low, there could be ambient cured, or semi-cured overspray which lingers in the spray booth. This overspray could contaminate the target products before they are removed from the spray area. 
  • The size of the booth and the target product also play a role in the need for differing air velocities. 
  • The distance between the target product and the face of the filter plenum contribute the impact of differing air velocities. 
  • Full down-draft spray booths may require less air velocity since the laminar air flow pattern is vertical thus utilizing gravity as a natural overspray removal process.
  • If air velocity is too low, the spray booth may experience “roll-back” where the overspray bounces back from the filter plenum towards the target product, operator, or booth openings. 
  • Insufficient air velocity can result in the discharge of overspray outside of the spray booth’s footprint. 
  • In a closed, pressurized spray booth, high air velocity could indicate an overly negative spray booth environment.
  • End users with closed, pressurized spray booths must determine is their application is better suited for negative, or positive spray booth pressure before isolating optimum air speed velocity across the face of the target products. 
  • For the safety of all workers, end-users should always follow all MSDS and technical information for the atomized coatings used in their application when making decisions about spray booth air velocity. If necessary, the use of an industrial hygienist is recommended. 
  • End-users should always consult with their air permitting requirements, and any local, state, or federal guidelines regarding worker safety and/or the outside environment. 

Chemco provides the widest range of intake and exhaust filtration products in the industry. We have products for every type of liquid and powder coating system, regardless of Class of finishing or end-market.