Recently, the safety of workers in industries has emerged as an important issue. In particular, when the workers are exposed to gaseous or liquid acids, it can lead to a serious problem to the human body. In the previous studies, we investigated the application of halochromic dyes on a nylon fabric for an acid-detecting textile chemosensor. In this study, bromocresol green was selected as a pH-indicating dye and its dyeing, fastness, and acid-sensing properties on a wool woven fabric were investigated. Bromocresol green in an aqueous solution of pH 2-4 showed maximum absorption at 444 nm with yellow color, whereas the maximum absorption changed to 616 nm showing blue color in a solution of pH 6 and over. Color yields (K/S) of bromocresol green on wool were dependent on the dyebath pH. The wool fabric showed greenish blue color when dyed at pH 4-7. The color of wool dyed at pH 3 was yellowish green, and the color at pH 2 was olive. The percent exhaustion of bromocresol green on wool increased with decreasing the dyebath pH, and a high exhaustion value of 98-99% could be obtained at pH 2-4. When the control sample, dyed at pH 4, was immersed in a solution of pH 3.5-4, its original greenish blue color was maintained. When immersed in a solution of pH 2-3, the color changed into olive with exhibiting a big color difference. The soaping process did not affect the color fastness. The wash and dry cleaning fastness of the wool fabric dyed at pH 3-5 was very good. The dry and wet rubbing fastness were excellent.