Light propagation within N95 filtered face respirators: A simulation study for UVC decontamination

Area of Science:

• Optics
• Biomedical Engineering
• Materials Science

Background:

• Filtered face respirators (FFR) are crucial for infection control.
• Ultraviolet germicidal inactivation (UVGI) offers a potential method for extending FFR usability.
• Understanding UV light penetration through FFR materials is essential for effective UVGI.

Purpose of the Study:

• To numerically simulate Ultraviolet C (UVC) light propagation through seven distinct FFR models.
• To assess the suitability of these FFRs for Ultraviolet germicidal inactivation (UVGI).
• To provide data for optimizing UVGI protocols for FFRs.

Main Methods:

• Numerical modeling of UV light propagation using the FullMonte program.
• Determination of optical properties for the three dominant FFR layers via the inverse adding doubling method.
• Analysis of fluence rate volume histograms and minimum recorded fluence rates.

Main Results:

• Significant variation in UVC light penetration was observed across the seven FFR models.
• Fluence rate volume histograms and minimum fluence rates (nW cm⁻²) indicate differing UVGI efficacy.
• The study quantifies the required UV exposure times based on respirator properties and light source.

Conclusions:

• FFR suitability for UVGI is highly dependent on material optical properties and respirator design.
• UVGI presents an economical strategy for FFR reuse, but requires precise optimization.
• Careful selection of FFRs and illumination setups is critical for successful UVGI implementation.