1	Characterization and Control of Bacterial Contamination in HVAC Systems
2	Introduction Bioaerosols, suspended biological particulate matter in air of which some cause infectious diseases, have become a main cause of concern when dealing with indoor air pollution. These compounds can circulate through a building after being deposited outside near the air intake of a building’s heating, ventilation, and air conditioning (HVAC) system, or after being released inside the building and recirculated through the HVAC system. Ultraviolet Germicidal Irradiation (UVGI) can be used in order to damage the DNA of bioaerosols so they are unable to reproduce (inactivation).
3	Research Objectives Explore and compare bioaerosol sampling methods : Air Sampling Duct surface sampling Cooler condensate sampling (couldn’t achieve due to low relative humidity) Determine the effectiveness of UVGI within ductwork at inactivating bioaerosols.
4	Experimental Scenarios
5	Configuration of Test Chamber
6	Ductwork
7	Protocols Velocities in ductwork calibrated to achieve velocities consistent with typical air flows and isokinetic air sampling. Typical air flows in commercial buildings: 10-20% Outdoor Air/80-90% Recirculating Air Flowrates Achieved: 22% Outdoor Air/88% Recirculating Air Isokinetic Sampling: “equal-velocity” sampling nozzle tip opening area (A_n) and sample volumetric flowrate (Q_m) must be adjusted to obtain a velocity V_n = Q_m/A_n equal to the gas stream velocity (V_s) at the point of sampling
8	Protocols (cont.) Bacterial aerosol (Mycobacterium parafortuitum) generated for 90 min, air samples collected for the last 30 minutes. Biological air samples collected during sampling using duplicate impingers (AGI-30) filled with 30 mL of phosphate buffer solution (PBS) in each of the three sampling locations. Duct surface samples collected by placing pieces of sheet metal onto ductwork prior to experiments and collected afterwards to be rinsed with PBS in order to perform microbiological analysis similar to the air samples. UVGI lamps installed 0.38 m before sampling location in the recirculation duct.
9	Bioaerosol Quantification Collected microorganisms quantified by: Culturing (CFUs) Staining and direct counting with epifluorescent microscope
10	Room Aerosolization Experiments
11	Outdoor Aerosolization Experiments
12	Results Direct counts should not be affected by UVGI Plate counts should be reduced with UVGI CFU/DC Lower CFU/DC means more inactivation
13	Conclusions and Implications Duct sampling, while requiring less equipment, is not as sensitive as air sampling When bioaerosols were released outside, UVGI in recirculating air duct was successful in inactivating bacteria Our results show that in-duct UVGI lamps can be implemented in HVAC systems to reduce viable bacterial concentration within the duct Experiments with more controls are needed to determine whether UVGI in ducts is a dependable method of bioaerosol inactivation
14	Acknowledgements