p.1 

OAR Box 1415 

Prepped by Ollie Stewart 

Document Number: 

4) IV-E-4 

Docket Number: 

A-94-52 

Printed 7/15/2008 9:38:25 AM Sheet 4 of 130 
P.2 

A-WH-5Z 

iv-e-w 

Chuck Darvin 

Page 1 

CONTACT REPORT 

Person Calling: 

Person Called: 

Date of Contact: 

Keith Barnett 

U.S. Environmental Protection Agency 

OAnps/ESD/MICG 

919-541-5605 

Chuck Darvin 

USEPA/ORD 

919-541-7633 

December 17, 2001 

• - - - , \ ' ,• , 

••PAMH- i,u.v i 

Contact Summary: 

I called Chuck to ask about work he had done on stratification of PM and VOC in paint spray 

booths. 

Chuck stated that there were numerous reports and papers on the subject. Some ofthe work was 

incorporated into the Aerospace NESHAP for the filter test method. 

Some reports are "Demonstration of Split Flow Ventilation and Recirculation as Flow Reduction 

Methods in an Air Force Paint Spray Booth". EPA 600/R-94-214a or AL/EQ-TR-1993-0002. 

Demonstration of Paint Spray Booth Emissions Control Strategy using Recirculation/Partitioning 

and UV/Ozone Pollutant Emission Control. EPA 600/R-98-016a 

AWMA, June 1993. Demonstration of Paint Spray Booth Air Reticulation and Partitioning. 93-

RA-83C.03 

1997 AICHE meeting. Paint Spray Booth Design using Recirculation and Partitioning Ventilation 

14th Annual Army Environmental Symposium, 14 November 1989. USATHAMA. Stratification 

of Particulate and VOC Pollutants in Horizontal Flow Paint Spray Booths. 

Environmental Progress, Fall 98/99. Paint Spray Booth Design Using Recirculation and 

Partitioning. 

October 1997. Modern Painting and Coating 

Chuck and I briefly discussed the results of these studies. In vertical flow spray booths, the 

pollutants tend not to defuse laterally. You can see this visually by looking at the paint overspray, 

it tends to go straight down. Diffusion does not take place until the flow direction is changed 

(such as bend in the ducting). 

The same occurs in horizontal flow spray booths. The VOC does not diffuse, it remains stratified 

and moves horizionally to the exhaust. If the VOC source is close to the exhaust, the VOC does 
P.3 

Chuck Darvin 

Page 2 

not drop, but enters the exhaust at the same elevation it is released. The farther away the exhaust 

form the VOC source, the more it drops. 

I asked Chuck about the issue concerning OSHA regulations. Chuck said that in the 1970's 

OSHA took an NFPA regulation and incorporated it into their rules. The NFPA regulation says 

you can not recirculate, but not due to worker exposure concerns. It was to prevent 

concentrations getting high enough to reach the lower explosive limit (LEL)( e.g., explosion). 

Also, the regulation actually went on to say that you could recirculate if monitors were used to 

prevent reaching the LEL. Reaching the LEL is not a concern in paint spray operations due to the 

high air flows involved.. 

OSHA finally agreed that recirculation of paint spray booth exhaust would be handled as a de 

minimis violation unless the concentrations exceeded the safe levels for human exposure. A de 

minimis violation means the violation is entered in the inspectors's report, but no action is 

necessary (since the change does not affect the spirit ofthe regulation, it is not a finable violation 

ofthe rule). 

References suggested by Chuck on this issue are a letter from Susan Wyatt dated June 16, 1990, 

discussing de minimis violations; Industrial Ventilation, 21th edition, Manual of Recommended 

Practices; OSHA web site, OSHA directive 200-67, Instruction CPL 2.11 Oct 30, 1978. Also get 

a copy of NFPA 33, 1998 edition. Read this rule carefully about air recirculation. (Note that 

recirculation is not prohibited under NFPA codes).