Residence time of particles in indoor surface networks

Infectious microbes can spread rapidly from fomites (contaminated surfaces) via hand touch, with prolonged residence time on surfaces increasing transmission risk by extending exposure periods and/or involving more susceptible individuals. Existing studies have focused on decreasing microbial contamination, but not on the need for rapid removal from surface systems. This study introduces residence time as the time that a microbe spends within the surface system. We analyse both simple and generalised surface-touch networks using a compartmental model, predicting the spread and removal of infectious particles on surfaces. Our models reveal the physics of particle spread through four simple networks, yielding a closed-form analytical solution validated by laboratory data on a three-surface-touch network and Monte-Carlo Lagrangian simulations of a realistic network. Findings indicate that hands and surfaces, even without any particle source, can be highly contaminated. Transfer rates and removal rates are identified as the only influential parameters for equilibration time and the main influential parameters for residence time in a homogeneous network. Our theoretical model provides a solid foundation for investigating the fundamental physical process behind the transmission of infectious particles via the fomite route, contributing valuable insights for enhancing hygiene management in high-risk environments.