Control of Methylene Chloride—Furniture Stripping Dip Tank

Abstract

The furniture stripping industry has an estimated 21,000 workers who are employed by approximately 4000 small businesses averaging slightly over five employees each. Previous worker exposure studies have documented time-weighted average exposures to methylene chloride in the furniture stripping industry ranging from 300 parts of methylene chloride per million parts of air (ppm) to over 2100 ppm. This article describes an evaluation of a local exhaust ventilation system designed by researchers from the National Institute for Occupational Safety and Health (NIOSH) for furniture stripping dip tanks that can be used to control methylene chloride exposures to workers. The dip tank process makes up approximately 10 percent of the furniture stripping industry. (Ventilation systems for the major process, the solution recycle method, have been previously evaluated by NIOSH researchers and the information has been published elsewhere.) The ventilation system described herein is a two-sided slot hood with an exhaust flow of 2900 ft³min. After installation of this system at a small commercial furniture stripping and refinishing shop, air samples for methylene chloride were collected during furniture stripping operations. The geometric mean of personal exposures to methylene chloride was 13 ppm (during stripping only processes with no rinsing being done in the shop), which is less than the Occupational Safety and Health Administration (OSHA) proposed permissible exposure limit (PEL) of 25 ppm. In previous worker exposure evaluations at this shop, methylene chloride levels were approximately 2200 ppm with no ventilation system, and 230 ppm with an owner-designed ventilation system. With the slot hood in place, air samples for methanol, toluene, 1,1,1-trichloroethane, and perchloroethylene were all well below the NIOSH recommended exposure limit and OSHA PEL. The estimated cost of the system was $3500. Other furniture stripping facilities that utilize dip tanks could apply this type of ventilation system to reduce worker exposure to methylene chloride. Hall, R.M.; Martinez, K.F.; Jensen, P.A.: Control of Methylene Chloride—Furniture Stripping Dip Tank. Appl. Occup. Environ. Hyg. 10(3): 188–195; 1995.