Fluence rate and ozone production from far-UVC lamps - A perspective

Area of Science:

• Photochemistry
• Environmental Science
• Public Health

Background:

• Far UV-C lamps (≈222 nm) are proposed for continuous air and surface disinfection in occupied spaces.
• Their efficacy and safety depend on fluence rate, which is often confused with irradiance and inconsistently measured.
• Ozone production is a key photochemical byproduct of Far UV-C exposure.

Purpose of the Study:

• To clarify the radiometric foundations of fluence rate and distinguish it from irradiance.
• To provide a quantitative link between fluence rate and ozone production for Far UV-C systems.
• To establish a framework for evaluating the trade-off between disinfection efficacy and ozone risk.

Main Methods:

• Reviewing methods for calculating room fluence rate distributions and measurement limitations.
• Examining photolytic ozone generation at 222 nm using atmospheric chemistry principles.
• Introducing a normalized ozone formation coefficient to relate fluence rate to ozone production.
• Summarizing a steady-state indoor ozone model including ventilation and occupant effects.

Main Results:

• Accurate determination of fluence rate is crucial for Far UV-C system performance.
• A quantitative relationship between average fluence rate, pathogen reduction, and ozone concentration was established.
• The study highlights the trade-off between disinfection efficacy and potential ozone risks.

Conclusions:

• Fluence rate is the central design variable for Far UV-C air disinfection systems.
• Accurate fluence rate determination is essential for realistic system design and risk assessment.
• The presented framework aids in balancing disinfection benefits with ozone safety concerns.