The conditions in a HVAC system encourage growth of the bacteria that causes legionnaire’s disease. It can grow in a washer system - methanol or a surfactant keeps the bacteria from colonizing. Quaternary disinfectants(anything with n-alkylated ammonium chlorides or benzalkonium chloride as the active such as Clorox wipes or Lysol) are essentially surfactants that disrupt the cell walls of most bacterium and virii. Those have demonstrated antimicrobial performance.Be interested to see how many people end up with Legionnaires Disease as a result of that practice. Similar situation that happened all over the UK about a decade ago.