If you are allergic to mold or duct mites, you probably already know that you should keep the relative humidity level in your home below 50% to avoid the growth of unwanted organisms. Mold and dust mites thrive in damp environments, and hot water extraction leaves carpet fibers damp. Mold spores can germinate after only 12 hours in hospitable conditions, and a mold colony may form in as little as a day.

Wet carpet cleaning methods often dampen the padding below the carpet, too, and the covered padding takes even longer to dry, providing ideal conditions for mold and mildew growth.