title: Should the placement of carbon monoxide (CO) detectors be influenced by CO's weight relative to air?
abstract: BACKGROUND
  Numerous states and localities have recently passed legislation mandating the installation and use of residential carbon monoxide (CO) detectors/alarms. Interestingly, there seems to be confusion about the optimal placement, if any, of CO alarms inside the home.
  
  
  OBJECTIVE
  It was the goal of this study to demonstrate the behavior of CO in air and to help provide a data-based recommendation for CO alarm placement.
  
  
  METHODS
  CO was calculated to be slightly lighter than air. An 8-foot-tall airtight Plexiglas chamber was constructed and CO monitors placed within at the top, middle, and bottom. CO test gas (15 L, 3000 parts per million) was infused at each of the three heights in different trials and CO levels measured over time.
  
  
  RESULTS
  Contrary to a significant amount of public opinion, CO did not layer on the floor, float at the middle of the chamber, or rise to the top. In each case, the levels of CO equalized throughout the test chamber. It took longer to equalize when CO was infused at the top of the chamber than the bottom, but levels always became identical with time.
  
  
  CONCLUSIONS
  As would have been predicted by the Second Law of Thermodynamics, CO infused anywhere within the chamber diffused until it was of equal concentration throughout. Mixing would be even faster in the home environment, with drafts due to motion or temperature. It would be reasonable to place a residential CO alarm at any height within the room.
authors.affiliation: Center for Hyperbaric Medicine, Virginia Mason Medical Center, Seattle, WA 98101, USA.
authors.forename: Neil B
authors.initials: NB
authors.lastname: Hampson
authors.forename: Todd G
authors.initials: TG
authors.lastname: Courtney
authors.forename: James R
authors.initials: JR
authors.lastname: Holm
mesh_terms: D000392:Air Movements; D002248:Carbon Monoxide / Q000032:analysis*; D002249:Carbon Monoxide Poisoning / Q000517:prevention & control*; D011482:Protective Devices; D013696:Temperature
chemical_list: D002248:Carbon Monoxide