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

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

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

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

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

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

Results of Preliminary Surveys

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

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

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

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

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

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

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

Comparison of Results

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

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

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

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

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

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.