As fragrances, air freshener preparations often include terpenes such as limonene. Borax is a natural cleaner and freshener, also known as a detergent booster. The balsam fir is also used as an air freshener and as incense. Baby powder can also be used as a shampoo, cleaning agent, and freshener. Glade Shake n' Vac is a powdered carpet freshener. Storax incense is used in the Middle East and adjacent regions as an air freshener. Glade's two main competitors in the air freshener market are Air Wick and Renuzit. Hippocrates used mastic for the prevention of digestive problems, colds and as a breath freshener. Ambi Pur is a brand of air freshener products owned by Procter & Gamble. It was the first brand to launch a plug-in liquid air freshener. Some bin models also include a small receptable for an air freshener. They have released other unique merchandise, including an air freshener. The first modern air freshener was introduced in 1948. The autographed edition also came with a limited edition air freshener. This type of product became the industry standard and air freshener sales experienced tremendous growth.