title: Development of novel cardboard filters very effective in removing airborne bacteria from confined environments.
abstract: OBJECTIVE
  Since bacterial pollution is more troublesome than other nonbiologic air pollutants, the need to control airborne micro-organisms has led to renewed interest in filter media for air filtration in indoor environments. Although mechanical filtration of aerosols by HEPA systems is the most common method for particle removal, these filters characterized by high efficiency usually reveal a higher drop in pressure and noise and are very expensive. On this basis, we aimed to develop novel, very effective air filters for removal of airborne bacteria from confined environments.
  
  
  METHODS
  Parallelepiped filters surrounded by a cardboard frame were manufactured by aligning strips of corrugated cardboard and were assessed in terms of airflow rate reduction. Cardboard filters were soaked in isopropanol or used untreated in in vitro experiments for assessment of their antibacterial effect against E. coli and in a testing chamber for assessment of airborne bacterial removal. The surface morphology of cardboard specimens was also investigated by Scanning Electron Microscopy (SEM).
  
  
  RESULTS
  Cardboard filters determined a very low decrease in airflow rate. Although specimens showed no antimicrobial behavior, untreated filters showed a maximum of 77% abatement of the airborne bacteria and the alcohol treatment of filters further increased their effectiveness by 14% probably because of their more convoluted surface.
  
  
  CONCLUSIONS
  This work disclosed corrugated cardboard-based filters as promising tools for the air treatment of indoor environments because of their excellent microbial abatement properties. Moreover, cardboard is lightweight, inexpensive, and eco-friendly material, and corrugated cardboard-based air filters are very simple in shaping, mounting, and replacing existing ventilation systems.
authors.affiliation: Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Italy. gabriele.candiani@polimi.it
authors.forename: Gabriele
authors.initials: G
authors.lastname: Candiani
authors.forename: Barbara
authors.initials: B
authors.lastname: Del Curto
authors.forename: Chiara
authors.initials: C
authors.lastname: Malloggi
authors.forename: Alberto
authors.initials: A
authors.lastname: Cigada
mesh_terms: D000389:Air Conditioning / Q000295:instrumentation*; D000391:Air Microbiology; D000393:Air Pollutants / Q000302:isolation & purification*; D001419:Bacteria / Q000302:isolation & purification*; D017753:Ecosystem; D004867:Equipment Design; D019544:Equipment Failure Analysis; D010209:Paper; D014462:Ultrafiltration / Q000295:instrumentation*
chemical_list: D000393:Air Pollutants