Biological contaminants include bacteria, viruses, mold spores, and allergens that grow and spread in HVAC systems when moisture and nutrients are present. Indoor levels can reach 100-1000 CFU/m³ (colony-forming units per cubic meter) in problem buildings. These contaminants cause infections, allergies, and asthma exacerbation in sensitive individuals.
Growth Conditions
Biological contaminants thrive in humid environments above 60% relative humidity and in stagnant ductwork with dust accumulation. Cooling coils, drain pans, and humidifiers become contamination sources if not properly maintained. Legionella bacteria specifically grows in cooling tower water between 20-45°C.
Prevention and Control
Maintaining humidity between 30-50% prevents mold and dust mite proliferation. HVAC filter upgrades to MERV 13 rating capture particles down to 3 microns. Regular duct cleaning every 3-5 years, UV light installation in air handlers, and drain pan treatment with biocides provide comprehensive biological contaminant control.