Please note: This summary is provided to help you understand the regulations. Consult the references provided for links to the full text of the regulations.
This section provides information about environmental regulations governing cleaning with petroleum-based solvents.
Other types of cleaning operations are covered elsewhere on TERC, including:
Who is covered by the regulations?
Any facility carrying out processes that involve cleaning with petroleum-based (non-water-based) solvents.
Examples include degreasers and solvent parts washers used to clean water-insoluble contaminants such as grease, oils, and carbon deposits from vehicle parts at maintenance operations.
The regulations also cover the use and disposal of solvent wetted rags to manually wipe soils from the metal surfaces (hand wiping).
What is the purpose of the regulations?
With all solvent cleaning processes there are two major environmental concerns:
The solvent can evaporate during use or storage. Exposure to concentrated vapors from these solvents can cause breathing problems and headaches.
Solvent cleaning processes generate wastes such as spent solvent, oil, sludge, sediment, used shop towels, and similar wastes that require disposal. Some wastes are considered particularly hazardous for health or safety (see box), and must be handled under specific rules.
Different solvents present different levels of risk:
Health effects: Some of the most toxic compounds that were once used as cleaning solvents have been phased out in response to environmental and workplace regulations introduced during the 1970s. Today, most petroleum-based parts washers use less acutely toxic materials, referred to as by designations such as "mineral spirits" or "Stoddard solvent." Although less toxic, organic solvents can still potentially present both workplace and environmental hazards.
Safety concerns: Some wastes pose a fire hazard because of solvents that evaporate at a low temperature and can be readily ignited. Cleaners with higher flashpoints (>140°F) are available to reduce the risk of ignition.
Two sets of regulations have been developed to address these concerns.
- Air emissions regulations, based on the Clean Air Act, cover solvent cleaning operations that use certain common, particularly toxic solvents.
- Solid waste regulations, based on the Resource Conservation and Recovery Act (RCRA), cover the disposal of wastes from solvent cleaning operations, and require that wastes with certain specified properties, or that contain certain specified materials, be handled as hazardous wastes.
The first part of this section covers regulations that apply to emissions of solvent vapors to the atmosphere. The second part covers regulations that apply to disposal of solid and liquid wastes that contain solvents.
Regulations for Air Emissions
Solvent vapor emissions regulations that affect the transportation sector are primarily contained in two standards, generally referred to as NESHAPs (National Emissions Standards for Hazardous Air Pollutants).
- One standard deals specifically with a category of solvents, called "halogenated." The rules specified in the standard apply to any facility that uses this type of solvent.
- Another standard applies to companies involved in the manufacture of aircraft or aircraft components. It applies to a smaller number of facilities, but it covers a larger number of solvents, in addition to halogenated solvents.
See the TERC pages on the Halogenated Solvent NESHAP and the Aerospace NESHAP for details on their requirements.
Many vehicle maintenance facilities operate self-contained solvent cleaning units that are serviced by a commercial provider. Often, such units contain solvents that are not covered under the Halogenated Solvent Cleaning NESHAP. However, special rules may apply to these types of units in some states.
In addition to the federal rules, states and regional air districts have established a variety of regulations that impact solvent cleaning. In general, these rules can be met by using add-on controls, modifying equipment, improving work practices, or upgrading to using a lower emitting solvent. See the State VOC Regulations page for more details.
Regulations for Solid and Hazardous waste
Solvent cleaning generates solid wastes, some of which may be considered "hazardous waste," a specific regulatory category that imposes special obligations for managing and disposing of the waste. It is the generator's responsibility to determine whether any particular waste falls under the "hazardous waste" category (see Hazardous Waste Determination). The most common wastes generated by solvent cleaning are:
- Spent solvents
- Used shop towels
Spent solvents are almost always a hazardous waste, as defined by the Resource Conservation and Recovery Act (RCRA). Most commonly used solvents have flashpoints below 140°F, making them highly ignitable. A spent solvent can also be a hazardous waste listed on the EPA hazardous waste list, which means that it contains organic solvents that have been identified as being hazardous (tetrachloroethylene, trichloroethylene, xylene, toluene, methyl ethyl ketone, and benzene). Spent solvents are also usually hazardous because they pick up toxic metals such as lead from parts and equipment cleaned in the parts washer.
Solvent parts washers generate sludge, which is usually hazardous because it contains toxic metals and solvents from the parts cleaned.
Solvent contaminated wipes (i.e., shop towels, rags, etc.) are also regulated under RCRA. However, the applicable rules for wipes changed in 2013, at least on the federal level. The "Solvent-Contaminated Wipes" rule conditionally excludes wipes that are contaminated with solvents from certain hazardous waste requirements. Specifically, the rule modifies RCRA regulations for solvent-contaminated wipes that are:
cleaned and reused at industrial laundries or dry cleaners, and
wipes sent for disposal to a municipal solid waste landfill or a solid waste combustor.
To be excluded, solvent-contaminated wipes must be managed in closed, labeled containers and cannot contain free liquids when sent for cleaning or disposal. Additionally, facilities that generate these wipes must comply with certain recordkeeping requirements and may not accumulate wipes for longer than 180 days.
Facilities that generate wipes should carefully read the Solvent-Contaminated Wipes rule (Federal Register, July 31, 2013) and refer to EPA summary and guidance information. Also, it is very important to note that authorized RCRA states are not required to adopt these conditional exclusions. Use the RCRA Hazardous Waste State Resource Locator to find the specific rules for your state and a point of contact at your state environmental agency.
Hazardous waste must be managed, stored, transported and disposed of in accordance with specific federal and state regulations. The exact rules applicable to a given facility depend on the quantity of hazardous waste generated each month. For example, "small quantity generators" have fewer requirements than large quantity generators. For more information see Hazardous Waste. Rules also vary somewhat from state to state. Use the RCRA Hazardous Waste State Resource Locator to find the specific rules for your state and a point of contact at your state environmental agency.
Best Management Practices (BMPs)
Most regulations tell you what you have to do to be in compliance, but they don't explain how to do it. That's where "best management practices" come into play. BMPs are proven methods that help you to get into compliance and stay there. The following BMPs are recommended for solvent cleaning.
- Wipe off parts with a rag or wire brush before soaking in parts washer.
- Do not clean parts unnecessarily.
- Reduce the quantity of solvent used by implementing a two-stage cleaning system. The first stage should clean the dirtiest parts. The second stage uses cleaner solvent for final cleaning and rinsing. When the cleaning solution in the second stage is no longer effective, it can then be used to replace the solvent in the first stage. Fresh solvent is then used to replace the second stage.
- Parts washers should have a recirculating feature with built-in filtration to continuously remove dirt and contaminants. This will extend the life of the solvent.
- Use drip racks or trays to help increase drainage from parts to minimize solvent loss.
- When not in use, solvent streams should be turned off and lids on parts washers should be kept closed to reduce evaporative solvent loss.
- Do not dispose of used solvent on the ground or in a storm drain
- Do not combine spent solvent with used oil.
- Contract with a solvent management company to supply and recycle solvent.
- Keep accurate records of solvent, wash water, sludge processing and disposal for three years.
Rule and Implementation Information for Halogenated Cleaning Solvents (EPA) - EPA lists numerous documents associated with the rulemaking.
How the Clean Air Act Affects Halogenated Solvent Cleaning Operations - Fact sheet published by the Michigan Department Of Environmental Quality.
Understanding regulations on solvent cleaning equipment (Virginia Regulatory Fact Sheet) - An overview of the regulations and alternatives for compliance.
National Emission Standards for Hazardous Air Pollutants (NESHAP) for Aerospace Facilities - Fact sheet provides an overview of the regulation and compliance alternatives.