ABSTRACT
This chapter focuses on substitution as a source control, substituting either a less hazardous manufacturing process for a more hazardous process or a less hazardous chemical for a more hazardous chemical. It discusses solvents categorized as either water-based (essentially nonvolatile), semi-aqueous solvents (low volatility), or volatile organic solvents. Semi-aqueous cleaners have some organic liquid components and may have more additives than aqueous cleaners but are still composed mostly of water. Semi-aqueous cleaners are not as environmentally beneficial as aqueous cleaners but often comprise a more cost-effective substitute for traditional organic solvents than aqueous cleaners. In general, the semi-aqueous cleaners have better solvency for a number of difficult contaminants such as heavy grease, tar, and waxes. Semi-aqueous cleaners may have a lower corrosion potential with water-sensitive metals. Substitutions among volatile chemicals are more complex than substitutions among nonvolatile or low volatility chemicals.
