The answer to 'upholstery cleaning smells bad' is that there are a few common causes, including improper cleaning techniques, residual soap or detergent, and mold or mildew growth. This can result in an unpleasant odor that lingers after the cleaning process.
Some common causes include using too much cleaning solution, not properly rinsing the fabric, or not allowing the upholstery to fully dry before use. Mold and mildew can also develop if the upholstery is not dried thoroughly. In some cases, the odor may be due to trapped dirt, pet hair, or other debris that was not removed during the cleaning.