The answer to 'deep cleaning smells bad' is that a persistent foul odor after deep cleaning is often caused by trapped moisture, mold, or bacteria. Deep cleaning can dislodge and expose these problems, leading to unpleasant smells. Common causes include inadequate drying, poor ventilation, or pre-existing mold or mildew issues.
The solution typically involves addressing the root cause, such as improving airflow, thoroughly drying surfaces and materials, and using specialized cleaning products to eliminate odor-causing microbes. In some cases, you may need to call a professional cleaning or mold remediation service if the problem is severe or difficult to resolve on your own.