A New Method for the Validation of Ultraviolet Reactors by Means of Photochromic Materials

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

With COVID-19 N95 shortages, frontline medical personnel are forced to reuse this disposable-but sophisticated-multilayer respirator. Widely used to decontaminate nonporous surfaces, UV-C light has demonstrated germicidal efficacy on porous, non-planar N95 respirators when all surfaces receive ≥1.0 J/cm2 dose. Of utmost importance across disciplines, translation of empirical evidence to implementation relies upon UV-C measurements frequently confounded by radiometer complexities. To enable rigorous on-respirator measurements, we introduce a photochromic indicator dose quantification technique for: (1) UV-C treatment design and (2) in-process UV-C dose validation. While addressing outstanding indicator limitations of qualitative readout and insufficient dynamic range, our methodology establishes that color-changing dosimetry can achieve the necessary accuracy (>90%), uncertainty (<10%), and UV-C specificity (>95%) required for UV-C dose measurements. In a measurement infeasible with radiometers, we observe a striking ~20× dose variation over N95s within one decontamination system. Furthermore, we adapt consumer electronics for accessible quantitative readout and use optical attenuators to extend indicator dynamic range >10× to quantify doses relevant for N95 decontamination. By transforming photochromic indicators into quantitative dosimeters, we illuminate critical considerations for both photochromic indicators themselves and UV-C decontamination processes.

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

With COVID-19 N95 respirator shortages, frontline medical personnel are forced to reuse this disposable - but sophisticated - multilayer textile respirator. Widely used for decontamination of nonporous surfaces, UV-C light has germicidal efficacy on porous, non-planar N95 respirators when ≥1.0 J/cm^2 dose is applied across all surfaces. Here, we address outstanding limitations of photochromic indicators (qualitative readout and insufficient dynamic range) and introduce a photochromic UV-C dose quantification technique for: (1) design of UV-C treatments and (2) in-process UV-C dose validation. Our methodology establishes that color-changing dosimetry can achieve the necessary accuracy (>90%), uncertainty (<10%), and UV-C specificity (>95%). Furthermore, we adapt consumer electronics for accessible quantitative readout and extend the dynamic range >10× using optical attenuators. In a measurement infeasible with radiometers, we observe striking 20× dose variation over 3D N95 facepieces. By transforming photochromic indicators into quantitative dosimeters, we illuminate critical design considerations for both photochromic indicators and UV-C decontamination.

Modelling and Multi-objective Optimisation of the VHP Pouch Packaging Sterilisation Process

Spouted pouches are being increasingly used in the beverage sector. However, aseptic packaging technology used for spouted pouches requires a highly complex sterilisation and rinsing process for the packaging materials before filling. This paper deals with the pouch packaging sterilisation process used in aseptic technology. A mixture composed of vaporised hydrogen peroxide and hot sterile air is injected into the package through a sterilisation nozzle. A CFD multicomponent model in ANSYS CFX (version 14.5) has been created and validated in order to simulate the real process. Based on this model, the paper aims to minimise hydrogen peroxide consumption and optimise the sterilisation treatment of the packaging. This issue has been approached using multi-objective optimisation software applied to CFD multicomponent simulations. The most suitable nozzle position inside the pouch has been established, as well as the optimal treatment time, concentration and flow rate of the sterilising mixture.