Personal Injury Law

Iowa Workers' Compensation - PERC - Part II - Drycleaning Controls 101

By Steve Lombardi

PERC Exposure Controls - The NIOSH study evaluated the primary working hypothesis that four general categories of drycleaning machines were capable of maintaining an 8-hour TWA personal exposure to PERC of less than or equal to 25 ppm.

The four general categories of drycleaning machines evaluated were: 1. Transfer machines. 2. Vented and nonvented dry-to-dry machines. 3. Machines with refrigerated condensers and/or carbon adsorbers. 4. "Fifth generation," nonvented, dry-to-dry machines, having residual controls.

Two Basic Types of Drycleaning Machines -- Two basic types of machines are generally used in drycleaning: transfer and dry-to-dry.

Transfer machines are older, less expensive, and require manual transfer of solvent-laden clothing between the washer and dryer, a source of high worker exposure. Dry-to-dry machines eliminate clothing transfer because items are processed in one step, entering and exiting the machine dry. Transfer machines process more clothing than comparably sized dry-to-dry machines because the process time is approximately half that of a dry-to-dry machine. To compensate, some owners of dry-to-dry machines reduce the cycle time, thereby increasing productivity. Such practices can also increase exposures that result from unevaporated residuals in the drycleaned clothing.

Transfer machines are generally vented, but dry-to-dry machines can be vented or nonvented. Vented dry-to-dry machines exhaust residual solvent vapors directly into the atmosphere or through some form of vapor recovery system, usually during the aeration process. Nonvented dry-to-dry machines are essentially closed systems, which are open to the atmosphere only when the machine door is opened. These machines recirculate the heated drying air through a vapor recovery system and back to the drying drum, eliminating the aeration step. Unfortunately, significant concentrations of PERC remain in the drum at the end of the cycle.

Full post as published by Des Moines Personal Injury Lawyer on February 03, 2008 (boomark / email).