Abstract: A device, system, and method for neutralizing pathogens in air flow. The device includes disinfectant-generating reactants (a disinfectant catalyst) within an outer layer. In use, liquid (such as water) is delivered to the disinfectant catalyst/outer layer modules. In an embodiment, the supplied liquid and disinfectant-generating reactants (of the disinfectant catalyst) combine, and generation of a disinfectant commences. The disinfectant in vapor phase is generated and diffuses through the outer layer of the module and is delivered to the air flow within an apparatus or system (e.g., HVAC system, electrostatic precipitator, etc.).