Determination of CADR of virus-inactivating air purifiers by surrogate virus plaque assay

The microbiological clean air delivery rate (mCADR) [m^3/h] of a mobile air purifier (MAP) that inactivates airborne viruses instead of filtering particles can be determined by sampling air in a test room with a test aerosol that contains active surrogate viruses such as bacteriophages (e.g. Phi6) and subsequent analysis of virus activity by plaque assay. We present an evaluation model, which is feasible to determine the mCADR of a MAP in a two-phase testing procedure with continuous Phi6 release while the MAP is active. The calculated concentration trend fits very well with experimental particle measurements. The evaluation model is applicable for normative purposes like the certification of MAPs. In addition, the formulas could be used for computer modelling of the concentration trend or estimating the steady state concentration of airborne pathogens, e.g. in classrooms or offices.