Drycleaning Solvents: Properties, Hazards, and Regulations

Drycleaning Solvents: Properties, Hazards, and Regulations

Every drycleaning operation is built around a solvent—the fluid that dissolves oils, greases, and soils from fabric without using water as the primary cleaning agent. Choosing and managing that solvent correctly determines how well garments clean, how safe the workplace is, and what regulations apply to your shop. This lesson compares the four main solvents in today's industry: perchloroethylene (perc), petroleum hydrocarbon, GreenEarth D5 silicone, and liquid carbon dioxide (CO₂).

What Makes a Good Drycleaning Solvent?

Two key numbers describe how a solvent performs:

KB (Kauri-Butanol) value measures solvency power—how aggressively the fluid dissolves oily soils. A higher KB value means stronger solvency. Think of it like the "horsepower" of the solvent. Perc has a KB value in roughly the 90s, making it the strongest cleaner of the group. Hydrocarbon solvents typically fall in the 25–35 range, offering gentler solvency. GreenEarth D5 silicone sits in the low-to-mid 20s range. Liquid CO₂ has very low solvency on its own and relies on agitation and sometimes small amounts of detergent to clean effectively.

Vapor pressure tells you how readily the solvent evaporates at room temperature. Higher vapor pressure means more vapor in the air, which increases both inhalation risk and the chance of reaching a flammable concentration. Perc has moderate vapor pressure; hydrocarbons vary by formulation but are generally low to moderate; D5 has very low vapor pressure; and liquid CO₂ operates under pressure in a sealed system, so vapor exposure in normal operation is minimal.

The Four Major Solvents

Perchloroethylene (Perc / PERC / tetrachloroethylene) has been the industry standard for decades. It cleans powerfully, does not burn, and dries quickly. However, it is classified as a Hazardous Air Pollutant (HAP) under the federal Clean Air Act and is regulated under the EPA's National Emission Standards for Hazardous Air Pollutants (NESHAP) for dry cleaners. OSHA sets an 8-hour time-weighted average (TWA) permissible exposure limit (PEL) for perc; workers must not exceed this limit, and engineering controls such as closed-loop machines, refrigerated condensers, and carbon adsorbers are required or strongly recommended. Perc is also listed under several state environmental programs as a potential carcinogen, and many states have enacted phase-down or phase-out timelines beyond federal requirements. Flash point: none—perc is nonflammable.

Petroleum Hydrocarbon Solvents (branded names include DF-2000, EcoSolv, and others) are refined petroleum fractions. They are combustible, with flash points typically above 140 °F (Class IIIA combustible liquids under NFPA classifications), so fire-safe machines and proper storage are mandatory. Hydrocarbon solvents are not classified as HAPs under the Clean Air Act, which significantly reduces federal air-permit burdens. However, they are still volatile organic compounds (VOCs) subject to some state air rules. Their lower KB value means they may not remove heavy soils as effectively as perc without additional detergent chemistry.

GreenEarth D5 (Decamethylcyclopentasiloxane) is a silicone-based solvent. It is gentle on fabrics, odorless, and not classified as a HAP. D5 has an extremely low KB value and very low toxicity, making it attractive for delicate garments. Its environmental status has been subject to ongoing review regarding aquatic persistence, so operators should check current EPA and state guidance. Flash point is generally above 170 °F, so fire risk is low but not zero—proper handling is still required.

Liquid CO₂ operates at high pressure in fully enclosed machines. It produces no VOC emissions during normal operation and leaves no solvent residue on garments. Because the system is sealed, employee vapor exposure is extremely low. CO₂ machines have a high capital cost and require staff trained in pressurized-system safety. Solvency is the lowest of the group, so pre-spotting and specialized detergents are important parts of the process.

Hazard Communication and SDS Requirements

Under the OSHA Hazard Communication Standard (HazCom), every chemical used in a workplace must have a Safety Data Sheet (SDS) available to employees at all times. An SDS has 16 standardized sections. The sections most critical for drycleaning solvents include: Section 1 (Identification), Section 2 (Hazard Identification), Section 8 (Exposure Controls / PPE), Section 13 (Disposal Considerations), and Section 15 (Regulatory Information). Employers must train workers to read and use the SDS before exposure begins.

Required PPE varies by solvent. Perc typically requires chemical-resistant gloves (nitrile or equivalent), eye protection, and respiratory protection if engineering controls cannot keep exposures below the PEL. Hydrocarbon solvents require similar glove protection and eye protection; respiratory protection depends on vapor concentration monitoring. For any solvent, never eat, drink, or smoke in the work area.

Regulatory Overview

Federal oversight comes from two main agencies. The EPA regulates air emissions and environmental disposal under statutes including the Clean Air Act and RCRA (Resource Conservation and Recovery Act). The OSHA regulates workplace exposure limits, hazard communication, and PPE. Some states have additional requirements—California's regulations on perc, for example, are stricter than federal minimums. Always check your state environmental agency rules in addition to federal standards.

Safety Reminder

When handling any drycleaning solvent: ensure adequate ventilation, use the correct PPE listed on the SDS, never pour solvents down drains, and store solvent containers away from ignition sources (critical for hydrocarbons). In an emergency—spill or leak—follow the SDS emergency procedures and evacuate if directed. Report any skin or eye contact immediately and refer to first-aid guidance in Section 4 of the SDS.