Biological pollutants include mold, bacteria, viruses, dust mites, and pet dander. These contaminants can thrive in indoor environments, especially in areas with high humidity or inadequate ventilation. They pose health risks, triggering allergies, asthma, respiratory infections, and other illnesses. Additionally, some biological pollutants produce unpleasant odors, further compromising indoor air quality. Proper ventilation, humidity control, regular cleaning, and maintenance help mitigate the presence of biological pollutants, ensuring a healthier indoor environment.