Engineering Controls for Furniture Strippers to Meet the New OSHA PEL for Methylene Chloride

1. Engineering Controls for Furniture Strippers to Meet the New OSHA PEL for Methylene Chloride Cheryl Fairfield Estill, Daniel S. Watkins, Stanley A. Shulman, Robert W. Kurimo, Ronald J. Kovein National Institute for Occupational Safety and Health Centers for Disease Control and Prevention

2. Methylene Chloride OSHA PEL • PEL reduced to 25 ppm • Action level of 12.5 ppm • exposure monitoring • medical management • April 10, 2000 • effective date for furniture strippers

3. Study Goal • To design engineering controls to reduce employee exposures to below the 25 ppm PEL

4. Furniture Stripping • Methylene chloride, methanol, toluene • One employee • Alternates between two workstations • stripping, 40% of time • rinsing, 44% of time

5. Previous Ventilation Design • 1991 study at this facility • Local exhaust ventilation • strip tank only • two slots, front and back • Exhaust volume • 2900 cfm • Employee exposure • 59 ppm

6. Four Preliminary Surveys • Survey 1, Aug ‘97 - test existing system, • unrestricted make-up air • Survey 2, Mar ‘98 - test existing system, • no make-up air • Survey 3, Jun ‘98 - upgrade and clean stripping area ventilation • Survey 4, Jul ‘98 - add rinsing area ventilation

7. Results of Preliminary Surveys

8. Final Survey Ventilation Design • Changes to Stripping Tank • 60° transition piece • new fan • larger ductwork • eliminated elbows in ductwork

9. Ventilation Design • Rinse Area • ½ HP axial fan • Enclosure - 3 sides and a top • swivel table

10. Ventilation Results • Stripping Tank • exhaust volume 2700 cfm • slot velocity 2600 fpm • Rinsing Area • exhaust volume 2100 cfm • face velocity 120 fpm

11. Methods • Breathing zone samples - one employee • Area samples, stripping and rinsing area • Bulk solution samples • OSHA Method 80 (ORBO tubes) • Two sampling days • 10 - one hour samples

12. Methods • Employee Training • Employee watched a one-hour video • Talked with employee about work practices • Stripping Solution • Height of stripping solution • Paraffin wax

13. Results • Stripping solution - 14 inches from top • Paraffin wax was added • Methylene chloride content was 50% Preliminary Survey 4 Final Survey

14. Results - Final Survey • Two runs were eliminated. • Geometric mean - 8 ppm • Upper confidence limit - 13 ppm

15. Comparison of Results

16. Factors Which Reduced Exposure to Below PEL • Local ventilation • Stripping solution height, paraffin wax • Employee training

17. Local Ventilation Note: No ventilation measurements were taken during Survey 2.

18. Stripping SolutionEmployee Training • Solution in the tank must be kept high. • Paraffin wax must be used in the solution • Employees must be trained

19. Costs $6840 $4545 $4340 Operating costs of make-up air system - $1000/year

20. Limitations • Methylene chloride concentration - 50% • Costs are high • Three factors • Ventilation • Stripping Solution • Work Practices • It may take many iterations to reduce exposures to the PEL

21. Conclusions • Technically feasible to reduce exposures to below the OSHA PEL • Use of this system can reduce exposures below the action level. • The 95% upper confidence level was 13 ppm, slightly above the action level.