Bipolar Ionization Did Not Reduce Airborne Bacteria in a Lecture Hall

Area of Science:

• Environmental Science
• Microbiology
• Indoor Air Quality

Background:

• Air ionization is proposed for inactivating airborne pathogens.
• Real-world effectiveness of ionization for disease control is unverified.

Purpose of the Study:

• To evaluate the impact of an in-duct bipolar ionization system on airborne particles and culturable bacteria in a lecture hall.

Main Methods:

• Ion concentrations and aerosol particle concentrations were measured.
• Bioaerosol samples were analyzed for total bacteria (16S rRNA gene copies) and culturable bacteria (CFUs).
• The ratio of CFUs to 16S rRNA gene copies was used to assess bacterial reduction.

Main Results:

• No significant differences in positive ion concentrations were observed.
• Negative ion concentrations were lower when the ionizer ran at a constant fan speed.
• No significant difference in the CFU to 16S rRNA gene copy ratio was found, indicating no reduction in culturable bacteria.

Conclusions:

• The tested bipolar ionization system was not effective at reducing culturable airborne bacteria in the studied lecture hall.
• Further research is needed to verify the efficacy of ionization technologies in real-world settings.