Dry cleaning allows garments to be cleaned in a manner that reduces damage to fabrics which is common in home-laundering processes that use water, detergent, agitation, and heat to clean the material. In certain fabrics, such as silk, rayon, and wool, the home-laundering process causes dye bleeding and fiber shrinkage or expansion. During the dry-cleaning process, garments are immersed in a type of liquid that causes the fabric to become wet but does not saturate or damage the fibers of the cloth. During this process, the fibers remain in their original state without water saturation, which reduces or eliminates damage to dyes and fibers.

Chemistry

Dry cleaning is a chemical-dependent operation. Each type of dry cleaning uses a blend of chemicals, detergents, and additives for cleaning. Spot or stain-removal operations are also heavily chemical dependent. Table 1 below outlines perchloroethylene(perc) and petroleum solvent operations and materials used.

Table 1

Type of operation	Perc operations	Petroleum solvent operations	Spot or stain removal
Materials used	Tetrachloroethylene	Stoddard solvents	Spot and stain removers containing chlorinated and aromatic hydrocarbons
	Water	Detergents
	Detergents	Additives
	Additives	Filter cartridges	Ammonic detergents
	Filter cartridges		Emulsifying, dispersing, and pH controlling agents

Equipment

Perc dry-cleaning equipment has evolved over time into four generations of equipment. The first generation consists of separate washers and dryers, commonly called transfer machines. Transfer machines required the transfer of clothing from the washer to the dryer. These machines were the industry standard until the 1960's when the second generation of dry-cleaning equipment combined the washer and dryer into one unit called a "dry-to-dry" machine. These units required less space and labor. Dry to dry machines also reduced solvent loss and employee exposure to cleaning solvents. Second-generation units were designed to emit residual vapors to the atmosphere or a separate control device.

Third-generation perc equipment, developed in the late 1970's, were closed-loop, dry-to-dry systems. Third-generation machines were equipped with integrated refrigerated condensers to further reduce emissions. Fourth-generation added additional controls that recycle the air in the machine.

Petroleum dry cleaning equipment has evolved less over time. Petroleum dry-cleaning machines are also divided into transfer and dry-to-dry machines. Vapor-recovery equipment ranges from standard dryers that do not recover any vapor to recovery units that use condensers. Both conventional (water-cooled) and refrigerated condensers are used.

Process Flow

Garment and fabric cleaning consists of several basic steps. Garments are first received from the customer, then inspected, pre-treated for stains, and sorted by color and fabric. Garments are then machine-washed in a solution of cleaning solvents. After washing, the cleaning solution is drained, and the garments are spun to extract remaining solvent. Garment drying is done with a combination of aeration, heating, and tumbling. Once dried, garments are removed from the drying equipment and inspected. If stains remain, the clothing is washed again. When cleaning and drying are completed, garments are finished by being pressed, either on tables or pressing forms, and are prepared and stored until pickup.

Specific dry-cleaning processes depend on the chemicals used, but in general, process steps are the same and are represented in the process map (Figure A) illustrated below. Figure A represents the most basic level of the process map. Click on each section of Figure A for detailed process maps of the perc ?dry-to-dry? machine cleaning process. Detailed maps are condensed from those compiled by Los Alamos National Laboratory and available in full at the Green Zia Website in their Environmental Excellence Program guide to the Dry Cleaning Industry.

Figure A

Figure B

B.1 Clothing Received at Counter

Clothing is received at the counter, where tags are added to individual pieces of clothing. This step generates wastes such as torn tags, pins, staples and various other wastes from the customer?s clothing. Also, clothing not properly identified may wind up as lost or unclaimed clothing.

B.2 Clothing Moved to Cleaning Area

Clothes are moved to the cleaning area and are inspected for stains.

B.3 Clothing Sorted by Color and Type

Once the clothing is in the cleaning area, employees sort it by color and type. The employee also decides which washing method should be used for each garment. Delicate garments are sometimes segregated and hand washed.

B.4 Clothing Weighed for Loading in Machine

Employees weigh the clothing before loading it into the machine and set the machine based on weight of load. Properly weighted loads may increase solvent cleaning efficiency.

Figure C

C.1 Dry-to-Dry Machine with Built-In Refrigerated Condensers

In this process, the washer and dryer are integrated into one unit. The clothes are washed with a mixture of perc and detergent. The cleaning process generates a waste which is comprised of a mixture of solvent, water, and detergent. Used solvent is recycled through a closed-loop distillation unit where it is reclaimed and recycled back into the cleaning process. During cleaning, some solvent vapors are lost to the atmosphere as employees open the machine door. Wastes generated include damaged clothing, vapor loss, lost buttons, and lint. Water is separated and sent through an evaporator.

C.2 Inspection/Final Spotting Operation

Once the clothes are dry, they are taken out of the dryer and inspected. Clothes that are not sufficiently cleaned are spotted and cleaned again. The spotting operation includes removing stains by using chemicals, steam, and scrubbing. This process generates small amounts of chemical sludge waste.

C.3 Sort and Hang Clothes for Pressers

Clothing is placed on hangers and sent to the pressing area. Some solvent vapors may be released at this point.

Figure D

D.1 Move Clothes to Pressing Area

Employees prepare and move the clothes to the pressing area. Losses associated with this process include dropped clothing and clothing with lost tags.

D.2 Pressing Operation

Clothing is pressed either on tables or pressing forms. Wastes or losses include energy and water in the form of steam and broken buttons or damaged clothing from pressing.

D.3 Wrapping Operation

Employees prepare clothing for customers by hanging the clothes on hangers, batching them by customer order, wrapping them in plastic, and twisting the tops of the plastic wraps with twist ties. Wastes include torn plastic, bent hangers, dropped clothing, or clothing placed out of sequence.

Figure E

E.1 Clothing Storage

During this process, clothes are moved to the storage area. Losses may include energy and floor space required to maintain the storage area. Potential losses include clothing that is never retrieved or clothing that has lost its identification tags.

E.2 Clothing Retrieval

Clothing is retrieved at the counter. Losses may include customer dissatisfaction with cleaning quality. The customer may also find the clothing not clean enough and request that the dry cleaner repeat the process.

Dry Cleaning Wastes

Dry-cleaning operations generate wastes and emissions from many sources. Table 2 outlines the types of wastes and emissions that are common to dry-cleaning businesses and provides examples of each. Residuals from industrial dry-cleaning operations may also contain various aromatic and chlorinated solvents, oils and greases, and other hazardous materials from the rags and clothing cleaned.

Table 2

Release medium	Wastes and Emissions
Air	Solvent spills fugitive Leaks from piping Vapor released when transferring or removing clothes from machines Vapor release from clothes dryers Residual vapor release from clothes after they are removed from the dryer
Water	Water from separator
Hazardous/solid waste	Residue from solvent spills Spent solvents Spent carbon and cartridges for carbon adsorbers Filters, filter powder (muck), and filter media Rags from solvent cleanup/spillage Surplus chemicals