Aqueous Cleaning Solutions Used In Degreasing Operations

Organic Solvent Degreasing

District Rule 4662 – Organic Solvent Degreasing Operations, was developed to help reduce emissions of volatile organic compounds (VOC) and hazardous air pollutants produced from degreasing operations, in which an enclosure or device is used for removing dirt, oil, grease and other contaminants.  Effective September 21, 2008, the VOC content of cleaning solutions used in most degreasing operations is limited to 25  grams of VOC per liter of solution.

Petroleum-based solvents, such as mineral spirits, contain VOCs that evaporate into the air during the cleaning process.  These emissions contribute to smog formation and may be toxic when inhaled.  Using low-VOC cleaning materials can help reduce smog, operating costs, and worker exposure to hazardous chemicals.

Aqueous Cleaning Solutions

The most common and effective cleaning solutions available that meet the VOC limit are water-based or aqueous cleaning solutions, which contain little or no VOCs.  Other options, such as cleaning solutions utilizing non-VOC solvents, may also be available.

Some cleaning solutions are general, all-purpose cleaners while others are designed to work best in certain applications. Your supplier should have information available to assist you in finding a cleaning solution that meets your cleaning needs and complies with the VOC limit. The South Coast Air Quality Management District (SCAQMD) has certified many complying products as “Clean Air Solvents”.

New Degreaser Equipment

Because aqueous cleaners are generally not compatible with traditional solvent cleaning equipment, new degreaser devices will be needed.  Aqueous cleaners require heat, agitation, and detergent action to break down grease and solids into smaller particles. 

Some smaller devices are “sink-top” units where an operator washes parts by hand as the cleaning solution is recirculated through a wand or a brush.  Others are enclosed units that operate like a dishwasher. Manufacturers and distributors have a wide variety of equipment available to choose from. It is important to choose a device designed for your specific cleaning application.


The recommended method of disposal is by means of a registered hazardous waste hauler.  Even though the newer-style cleaning solutions are water-based, they may not be dumped into a storm drain, gutter, or street.  Spent cleaning solutions may qualify as hazardous waste after extended use due to the accumulation of metals, oils, grease and sludge.  Like petroleum-based solvents, they must be disposed of in accordance with applicable wastewater and waste disposal regulations.

Local water sanitation districts may allow treated cleaning solutions that are free of pollutants to be discharged into the sewer provided that specific wastewater requirements are met.  A permit form the California Department of Toxic Substances Control may also be required.  For more information, please contact your local water sanitation district.


Current information suggests that using aqueous cleaning solutions may result in cost savings.  They are less expensive than petroleum-based solvents and require less frequent changing.  Some operators have also reported labor savings when utilizing automated cleaning equipment.


Rule 4662 specifies several exemptions that allow the use of solvents and cleaning materials containing more than 25 grams of VOC per liter of solution.  These exemptions apply to:

Small Units

    • One cleaning unit per building.  The unit must have an open top surface area of less than one square foot, a capacity of less than two gallons, and be equipped with a cover.

 Specialized Applications

    • Electrical
    • High precision optics
    • Aerospace and military cleaning of solar cells, laser hardware, fluid systems, and space vehicle components
    • Components used solely in research and development programs and laboratory tests in quality assurance laboratories

To determine whether your degreasing operation is exempt from the VOC limit, please review Rule 4662 or contact the Small Business Assistance at the regional office nearest you.