Engineering Controls Database
Control of Solvent Exposure during Furniture Stripping
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Potential chemical hazards in the furniture stripping industry are found primarily during the handling, stripping, and rinsing of the furniture. The major routes of entry of methylene chloride and other solvents into the body include inhalation of vapors and adsorption of the liquid through the skin. Methylene chloride can be inhaled when vapors are in the air. Inhalation of the methylene chloride vapors is generally the chief source of exposure. Methylene chloride evaporates quicker than most chemicals. The odor threshold of methylene chloride is 300 ppm. Therefore, once you smell it, you are being overexposed. Pouring, moving, or stirring the chemical will increase the rate of evaporation. Methylene chloride can be absorbed through the skin either by directly touching the chemical or through your gloves. It can be swallowed if it gets on your hands, clothes, or beard, or if food or drinks become contaminated. |
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Health effects studies of methylene chloride exposure have focused on four areas: effects on the central nervous system, effects on cardiovascular morbidity and mortality, induction of cancer in exposed workers, and reproductive effects. At airborne concentrations greater than 500 ppm over short periods of time, vapors are irritating to the eyes, upper respiratory tract, and mucous membranes. Other symptoms of high exposure are dizziness, headache, giddiness, stupor, irritability, numbness, tingling in the arms and legs, and lack of coordination. The occurrence of any of these symptoms indicates that there is exposure to high levels of the methylene chloride. A portion of inhaled methylene chloride is converted by the body to carbon monoxide, which can lower the blood’s ability to carry oxygen. Repeated contact can cause dry, scaly, and cracked skin. Direct contact with the liquid can cause skin burns. Methylene chloride is also a mild narcotic. Methylene chloride has been shown to cause cancer in certain laboratory animal tests. The available human studies do not provide the necessary information to determine whether methylene chloride causes cancer in humans. However, as a result of the animal studies, methylene chloride is considered a potential occupational carcinogen. There is also considerable indirect evidence to suggest that workers exposed to methylene chloride may be at increased risk of developing ischemic heart disease. Overexposure to methylene chloride while stripping furniture can cause death. Methanol, toluene, and acetone are also chemical health hazards found in the stripping fumes. Methanol has similar central nervous system effects to methylene chloride. Health effects for exposures to toluene above 200 ppm can cause changes in muscular coordination, reaction time, and production of mental confusion and irritation of mucous membranes. Acetone is one of the least toxic of the industrial solvents as far as health concerns. However, in cases of repeated exposure to low concentrations, complaints were received of headache, drowsiness, vertigo, irritation of the throat, and coughing. |
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Local exhaust ventilation can be used to control exposures to methylene chloride during furniture stripping processes. Local exhaust ventilation systems capture contaminated air from the source before it spreads into the workers’ breathing zone. If engineering controls are not effective, only a self-contained breathing apparatus equipped with a full facepiece and operated in a positive-pressure mode or a supplied-air respirator affords the necessary level of protection. A local exhaust system consists of the following: a hood, a fan, ductwork, and a replacement air system. Two processes are commonly used in furniture stripping: flow-over and dip tanks. For flow-over systems there are two common local exhaust controls for methylene chloride – a slot hood and a downdraft hood. A slot hood of different design is most often used for dip tanks. The hood is made of sheet metal and connected to the tank. All designs require a centrifugal fan to exhaust the fumes, ductwork to connect the hood and the fan, and a replacement air system to bring conditioned air into the building to replace the air exhausted. NIOSH researchers from the Engineering Control Technology Branch (ECTB) recommended, constructed, and installed the newly designed local exhaust ventilation system at a furniture stripping and refinishing facility in Cincinnati, OH. The ventilation system was constructed of galvanized sheet metal with reinforcement steel used on stress points in order to maintain the system’s physical integrity. A plenum was attached to the front end of the tank and to the slot hoods on each side of the tank in order to obtain even airflow distribution throughout the system. A 12” diameter duct ran from the center of the front plenum, through the wall of the building, into a fan located outside. For this evaluation, a portable, gasoline powered fan rated at 4100 cfm in free air was used.         |
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| 170-11-A; 170-12-A; 170-13B; 170-13C; 170-14-A; 170-16B; 170-17-A; 170-18A; 170-19-A; 170-20-A; 170-22-A; 170-23-A; | |
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