An air freshener is a product designed to mask or remove unpleasant room odors. These products typically deliver fragrance and other odor counteractants into the air. They do so through a variety of product formats, including aerosols, candles, potpourri, and gels. By the late 1990s, sales of air fresheners in the United States had exceeded several hundred million dollars per year. One the most successful new products are Glade Plug-Ins, which use heat generated by electric current to vaporize air-freshening ingredients.
Fragrance compounds have been used since antiquity to freshen air and mask odors. For example, the ancient Egyptians were known to use musks and other natural materials to scent their tombs. Over the last 2,000 years a variety of compounds, including numerous spices and floral extracts, have been used for their ability to impart a pleasant aroma. However, it was not until 1948 that the first modern air freshener was introduced. This product, using technology developed by the military to dispense insecticides, was a pressurized spray containing about 1% perfume, 24% alcohol or other solvents, and 75% chlorofluorocarbon (CFC) propellant. This was able to deliver a fine mist of fragrance that remained suspended in the air for a long period of time. This format of the product became the standard in the industry and sales grew tremendously. In the early 1950s, many companies began to add odor-counter-actant chemicals to their formulas. These were chemicals that were intended to actually destroy or neutralize offensive odors, as opposed to simply masking them with fragrance. Perfumery houses showed these active chemicals were capable of reducing a variety of unpleasant odors, such as cigarette smoke, urine and fecal odors, cooking smells, and amine odors typically associated with fish. Compounds used for this purpose included various unsaturated esters, longchain aldehydes and a few pre-polymers.
Over the next 25 years, aerosol air freshener formulas were modified to improve performance and reduce formula costs. But by the 1970s, the market significantly shifted away from aerosols, due to concerns about destruction of the ozone layer by chlorofluoro-carbons (CFCs). While reformulation by the aerosol industry has kept this product form from disappearing completely, alternate air freshener delivery forms have become increasingly popular. In the 1990s, a resurgence in potpourri and candles lead to a host of new air freshening products. For example, Kalib Enterprises Ltd.'s Potpourri, which contains a blend of dry spices and herbs, uses a battery-operated fan to circulate fragrance throughout the room. Arizona Natural Resources Inc.'s Crystal Candle division has introduced candles that kill odors, as well as aromatherapy candles that have specific therapeutic uses.
One of the most innovative, and popular, new formats is Glade Plug-Ins, manufactured by S. C. Johnson of Racine, Wisconsin. Plug-Ins use heat generated by electricity to spread fragrance through the air. It consists of a tiny plastic tray containing a gel-like fragrance concentrate. The consumer simply peels a multilayer barrier film from the top of the tray, leaving a permanent membrane layer that allows the fragrance to diffuse into
Plug-Ins consist of a small, plastic tray that holds a gel-like mixture of fragrance. This tray is inserted in a plastic unit equipped with electrical prongs that plug into a standard outlet. The electric current causes a heating element to warm up, vaporizing the volatile fragrance components. The fragrance in the tray lasts several weeks, at which time the consumer simply inserts a fresh tray. The product is designed with a variety of fragrance types to appeal to a wide consumer audience, including Honey-suckle, Mountain Meadow, Country Breeze, Powder Fresh, and Country Garden.
The lid stock of the fragrance tray is specially designed to both hold in the scent and let it out at a controlled rate. Utilizing patented technology, the proprietary laminated film is made with a multilayer barrier and a permeable membrane. S. C. Johnson Wax licensed patented film technology from American National Can that involves a removable barrier and a permanent membrane. The lid material, combined with the proper heat-sealing temperature, pressure, dwell time, and seal design, is designed for easy use by the consumer.
Compatibility between the fragrance formulation and the lid material is key to product performance. During testing, S. C. Johnson researchers further refined the formulations as they learned how they behave with films. Their suppliers also learned a great deal about improving their film technology. The film structure is applied in a one step process during a form-fill-seal operation. An angled piece of the film allows the consumer to easily peel off the outer film/foil barrier layer. The inside membrane, however, remains securely sealed to the tiny tray. As the fragrance is warmed, the membrane allows a continuous and regulated fragrance release. As fragrance is released, the concentrate cracks and dries out, visually signaling the consumer to replace the refill tray. The tray also features a patented ridge down its middle, which is used as a guide for inserting the tray into the warmer unit.
Even the carton that contains the product is unique. This innovative one-piece package went through more than 25 design modifications before fulfilling all marketing and manufacturing requirements. Specifically, it contains a special fifth panel, which secures the warmer unit and fragrance pack during packaging and point of purchase display. The carton features a polyester window that wraps around the side of the folding carton, so the consumer can see the electrical blades of the warmer unit. The carton is designed to show off the warmer unit and its blades, to display the fragrance pack, to easily fit on store shelves, to run on high-volume machinery, and to be reasonably priced.
The perfume oils used in preparing fragrance concentrate in the air fresheners can be divided into a variety of types. These include aldehydes, which are members of the synthetic fragrance group. When concentrated, aldehydes smell soapy or fatty; however, when mixed in the proper proportions with water, they develop a sweet, flowery smell. Green fragrances are fresh, having an odor similar to cut grass or plant stems and are also usually produced by synthetic perfume oils. However, natural sources of green notes such as galbanum, a tropical resin, or violet leaf oil are also used. Floral notes are some of the oldest and most popular fragrance components. Examples include jasmine-rose complexes blended with lilac and lily of the valley. Herbal-spice fragrance notes are also important components. Lavender, sage, moss, cinnamon, cloves, sandalwood, and cedar are used to provide these notes. Lastly, oriental fragrance notes may be included. These are sweet, heavy, and strong, and are often found in natural animal materials, such as musk. Specific examples of fragrance ingredients used in Plug-Ins include bergamot, bitter orange, lemon, mandarin, caraway, cedar leaf, cloverleaf, cedarwood, geranium, lavender, patchouli, lavandan, rose absolute, and many others. These can be mixed with a variety of synthetic fragrance components, such as aldehydes, ketones, esters, alcohol, terpenes, and so forth. These components are blended together, and mixed with a variety of gelling ingredients. The gel matrix that contains the fragrance can be an organic or inorganic system. These are typically prepared hot, and the fragrance is added as the product cools to preserve the integrity of the fragrance.
Quality control occurs at several stages during the manufacturing process. Incoming raw materials used in the fragrance and the gel matrix are assayed to ensure they meet specifications and provide the appropriate odor. The fragrances themselves must comply with regulations established by the California Air Quality Board (CARB), which is responsible for reducing the emission of volatile organic compounds (VOCs), which include the chemicals used in fragrances. By definition, VOCs have vapor pressures of more than 0.1 mm Hg-degrees (68°F or 20°C), or, if the vapor pressure is unknown, contain 12 or fewer atoms of carbon in the molecule. Other states, including New York, have passed similar legislation. These regulations have dramatically impacted the formulation of a variety of air freshener formulations. In addition, plastic components are inspected after molding to ensure they are free from sharp edges and cracks, which could compromise the package integrity.
The future of Plug-Ins, and other air freshener products, will be determined in part by the consumer product regulatory environment. Just as aerosol sprays were significantly impacted by VOC regulations, similar legislation could effect the fragrance ingredients allowed for use in other air freshener products. Furthermore, advances in packaging and dispersing technology will result in improved products to control room odors. For example, next generation of Plug-In type products are being developed at the time of this writing. These products are designed with a refillable chamber for fragrance oil.
Umbach, Wilfried, ed. Cosmetic and Toiletries. New York: Ellis Horwood, 1991.
McMath, Robert. "Whether the Cover or Kill, Air Fresheners Smell like Big Business." Brandweek 34, no. 8 (February 22, 1993):34.
Packaging 36, no. 3 (March 1991): 40.
— Randy Schueller