An experimental investigation of the performance of a Collison nebulizer generating H1N1 influenza aerosols

The performance of a Collison nebulizer delivering viable H1N1 influenza aerosols was assessed in terms of particle size distribution (PSD) and survivability of the virus upon generation. An H1N1 influenza virus preparation in egg allantoic fluid was diluted in sterile deionized water to a concentration of 3.4 x 10(6) TCID50/mL. The virus suspension was aerosolized at air flow rates of 2, 6 and 12 L/min using a 1-jet, 3-jet and 6-jet Collison nebulizer, respectively. A scanning mobility particle sizer measured the PSD of the viral aerosol after steady-state delivery times of 1, 15, 30, 45 and 60 min. After 60 min of continuous aerosolization, the viral titre was unchanged and the count median diameter (CMD) of the aerosol PSD was approximate to 38 nm for the 2 L/min flow rate, approximate to 35 nm for the 6 L/min flow rate and approximate to 33 nm for the 12 L/min flow rate. The CMDs were much smaller than the influenza virus (80-120 nm), indicating the aerosol distribution comprised mainly nonviable materials. The PSD produced by the Collison nebulizer exhibited a 20% increase in peak particle concentration after 60 min of continuous operation at 12 L/min. This progressive increase in particle counts may be attributed to a combination of evaporation and shear and impact stresses imparted on components by the Collison nebulizer. The possible slight loss in H1N1 influenza viability over the course of 60 min of continuous aerosolization at 12 L/min is consistent with previous bioaerosol studies using a Collison nebulizer.