Quantitative UV-C dose validation with photochromic indicators for informed N95 emergency decontamination

Area of Science:

• Medical Engineering
• Photochemistry
• Public Health

Background:

• Frontline medical personnel face N95 respirator shortages, necessitating reuse and decontamination.
• Ultraviolet germicidal irradiation (UVGI) is effective for decontaminating N95 respirators, but accurate dose measurement is challenging.
• Existing radiometers have complexities that hinder precise UVGI dose measurements on porous respirator surfaces.

Purpose of the Study:

• To develop and validate a photochromic indicator technique for precise UVGI dose quantification on N95 respirators.
• To enable accurate UVGI treatment design and in-process dose validation for respirator decontamination.
• To overcome limitations of qualitative readout and dynamic range in existing photochromic indicators.

Main Methods:

• Introduced a photochromic indicator technique for UVGI dose quantification.
• Addressed limitations of qualitative readout and insufficient dynamic range.
• Adapted consumer electronics for quantitative readout and used optical attenuators to extend dynamic range.

Main Results:

• Established that color-changing dosimetry achieves >90% accuracy, <10% uncertainty, and >95% UV-C specificity.
• Observed a ~20x dose variation across N95 respirators within a single decontamination system, a measurement difficult with radiometers.
• Demonstrated extended indicator dynamic range (>10x) for quantifying relevant N95 decontamination doses.

Conclusions:

• Photochromic indicators can be transformed into accurate, quantitative dosimeters for UVGI.
• The developed methodology illuminates critical considerations for both photochromic indicators and UVGI decontamination processes.
• This technique enhances the reliability and accessibility of UVGI dose measurements for N95 respirator decontamination.