The answer to 'carpet smells bad' is that there are several common causes, including pet accidents, spills, mold/mildew, and general dirt and odors. Symptoms can include a musty or unpleasant smell, as well as visible stains or discoloration. Solutions depend on the cause, but may involve deep cleaning, deodorizing, or professional carpet cleaning.
If the smell is mild, you may be able to address it with DIY methods like spot cleaning, shampooing, or using a carpet deodorizer. However, for more stubborn odors or widespread issues, it's best to call in a professional carpet cleaning service. They have the equipment and expertise to thoroughly clean and deodorize your carpets, removing any deeply embedded smells.