Commercial dry cleaning facilities include full service, retail operations located in shopping centers and near densely populated areas. The coin-operated sector of the market is typically associated with a laundromat that may provide either full service retail dry cleaning similar to the commercial sector, or customer-operated dry cleaning equipment. Most commercial dry cleaners are single facility "mom and pop" operations, although there is considerable variation in the size of these businesses. Classic family owned and operated commercial cleaners usually have two or three full time employees (including the owner) and perhaps some additional part time employees. A typical firm might consist of a single small store front operation, with customer pickup and delivery in front, and cleaning and finishing in the back.
Commercial dry cleaning is not a high profit business. As might be expected, commercial dry cleaners are distributed in a six to one urban to rural ratio as a result of the greater demand for dry cleaning in urban settings. The dry cleaning industry provides garment cleaning services and in most cases will provide related services such as clothes pressing and finishing. The dry cleaning process is physically very similar to the laundry process, except that clothes are washed in dry cleaning solvent instead of water.
Due to the low margins and the high internal loads very few are air-conditioned in summer and require little heat in winter. In addition to lighting and ventilation systems, energy is used for operating the cleaning machines, pressers, and solvent recovery. This may be in the form of electricity for motors and low pressure steam for pressing and some solvent recovery processes.
Fabric or garment cleaning consists of three basic functions: cleaning, drying, and finishing. Garments are pre treated for stains, and then machine washed in a solution of a solvent, soaps, and detergents. The solvent is extracted by first draining, and then spinning the clothes. Finally, the garments are dried through a combination of aeration, heat and tumbling, and then pressed. The store usually has one or two dry cleaning units (either a separate washer and dryer, or a combined "dry to dry" machine), and perhaps a water based laundry machine for shirts and other washables.
Two solvents now dominate the dry cleaning market: perchloroethylene (PCE) and petroleum solvents, although use of the latter is concentrated in the Gulf States of Texas and Louisiana. The use of flammable materials is widespread. Flammable gases and vapors (NFPA Standard 325) can be found in dry-cleaning plants. Adequate ventilation minimizes or prevents fires and explosions and is necessary regardless of other precautions, such as elimination of the ignition sources, safe building construction, and the use of automatic alarm and extinguisher systems.
In larger dry cleaning plants, adsorption can be used in recovering solvent vapors from dry cleaning. The components of a typical solvent recovery adsorption system uses two carbon beds. One bed is used as an adsorber while the other is regenerated with low-pressure steam. Desorbed solvent vapor and steam are recovered in a water-cooled condenser. Adsorption time per cycle typically runs from 30 min to several hours. The adsorbing carbon bed is switched to regeneration by an automatic timer shortly before the solvent vapor breaks through depending on the specific solvent and its concentration in the exhaust gas stream being stripped. Steam with only a slight superheat is normally used, so that it will condense quickly and give rapid heat transfer.
After steaming, the hot, moist carbon bed is usually cooled and partially dried before being placed back on stream. Heat for drying is supplied by the cooling of the carbon and adsorber, and sometimes by an external air heater. For most common solvents, the heat of adsorption is 40 to 60 Btu/lb-mol. Low-pressure steam consumption for regeneration is generally about 3.5 lb per pound of solvent recovered, but it can range from 2 to over 5 lb per pound of solvent recovered
Moving-Curtain Dry-Media Filters:
Special automatic dry filters are available for the removal of lint in dry-cleaning establishments. The medium used is extremely thin and serves only as a base for the buildup of lint, which then acts as a filter medium. The dirt-laden media is discarded when the supply roll is used up.
The hazards of the dry cleaning process (discussed below) related to the solvents indicate ventilation is vital and necessary. Ventilation is one of the most common engineering controls used to control emissions, exposures, and chemical hazards in the workplace. Other workplace environmental factors, including temperature, humidity, and odors are also controlled with non-industrial ventilation systems commonly known as heating, ventilating, and air-conditioning (HVAC) systems.
Related Technical Links:
Indoor Air Quality Ventilation Investigation. OSHA Technical Manual - Section III: Chapter 3 (1999, January 20), 26 pages. This chapter of the OTM contains information on several ventilation topics, including general concepts, health effects, standards and codes, investigations, etc.
Several hazards are associated with dry cleaning processes, including chemical, fire, and ergonomic hazards. Exposure to hazardous chemicals commonly used in dry cleaning shops can occur through skin absorption, eye contact, or inhalation of the vapors.
Perchloroethylene (PERC), a potential human carcinogen, is the most commonly used dry cleaning solvent. Symptoms associated with exposure include: depression of the central nervous system; damage to the liver and kidneys; impaired memory; confusion; dizziness; headache; drowsiness; and eye, nose, and throat irritation. Repeated dermal exposure may result in dermatitis.
Dry cleaning shops contain all elements necessary for uncontrolled fires: fuels, ignition sources, and oxygen. Potential combustible materials include furniture, garments, lint, and portions of the building. The greatest risk of fire and explosion exists if the dry cleaning shop uses a petroleum-based solvent in dry cleaning machines.
Ergonomic risks occur during garment transfer, pressing, and bagging. These activities, combined with a high work rate and frequency, may cause physical discomfort and musculoskeletal problems for workers. Disorders can include damage to tendons, muscles, nerves, and ligaments of the hand, wrist, arm, shoulder, neck, and back.