Functional analysis of a negative pressure airborne infection isolation canopy unit for the prevention of transmission of droplets and aerosols- An experimental study.

Background and Aims: This study describes the functional analysis of a negative pressure canopy unit developed to reduce infective aerosol and droplet spread in ad-hoc wards created to handle patients suffering from infective respiratory illnesses such as those recently encountered in the COVID-19 pandemic. Methods: An experimental study was conducted to verify the functional analysis of a canopy unit for the following variables: a) Quantitative and qualitative analysis of aerosol generation, b) Efficacy of canopy as containment device and c) Aerosol clearance from canopy over a period. We describe the process in the form of a problem statement, a discussion of design considerations (including Computer Aided Design modelling and a functional analysis of the system using a variety of simulated conditions which included various experiments for the purpose of testing the safety and efficiency of the system. We also incorporated Computational Fluid Dynamics analyses to assist us in design modifications of the unit using Euler-Lagrange approach for aerosol tracking. Results: As demonstrated by the series of experiments, it was seen that the aerosol load under the testing conditions reduced significantly. The canopy unit restricted the aerosol particles which either got adhered to the canopy walls or went into recirculation inside the canopy. In experimental conditions, the fan-filter unit was able to operate at >95% efficiency. Conclusion: This device exhibited 95-99% efficiency in eliminating aerosols which would reduce the exposure of health care workers to infective aerosols, which is not only specific to severe acute respiratory syndrome coronavirus (SARS-CoV)-2, but also to other airborne transmitted diseases.