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  • Resistance to UV inactivation: bacteria > viruses > fungal spores


  • Airborne rate constants tend to be higher in Air, under normal humidity: microbes are more vulnerable in Air, whereas microbes on Surfaces appear to have a certain degree of inherent protection


  • It is appropriate to treat Air and Surface UV disinfection together, since airborne microbes are often surface-borne and vice-versa


  • The inactivation rates of microbes on surfaces may vary depending on the type of surface. Some metals, like copper or silver, are naturally biocidal (殺生物) effects.


  • Water-based UV rate constants are substitutes for airborne rate constants



  • Surface rate UV constants may also be used conservatively in place of airborne data


  • Contaminated surfaces are often a source of airborne microbes, and airborne microbes often produce surface contamination.


  • Bacteria are 5 times (viruses are 3 times) more resistant in water than in air at low humidity. Water absorbs UV, i.e. it requires higher rates of UV dose to disactivate microbes, viruses and fungi.


  • Contaminated surfaces are often a source of airborne microbes


  • Airborne microbes often produce surface contamination


  • The interaction of Air and Surface contamination processes makes the issue of Air vs Surface disinfection almost inseparable:

    • Example: the disinfection of cooling coil surfaces removes mold spores from the coils and prevents subsequent aerosolization, thereby helping keep the air clean

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