Allergic reactions are the most common health problems associated with biological pollutants. Symptoms often include watery eyes, runny nose and sneezing, nasal congestion, itching, coughing, wheezing and difficulty breathing, headache, dizziness and fatigue. Dust mites have been identified as the single most important trigger for asthma attacks. Molds and dust mites thrive in areas of high humidity. Mold grows on organic materials such as paper, textiles, grease, dirt and soap scum.
Mold spores float throughout the house, forming new colonies where they land.
Dust mites thrive on dead human skin cells and in textiles such as bedding, carpeting and upholstery. When these textiles are disturbed during vacuuming, making beds or walking on carpet, the dust particles become airborne. Pollen, plant material that enters through windows or on pets, and animal dander also become airborne when disturbed. Infectious diseases caused by bacteria and viruses are generally passed from person to person through physical contact, but some circulate through indoor ventilation systems. There are no practical tests for biological contaminants for use by non-professionals.