title: Control of asthma triggers in indoor air with air cleaners: a modeling analysis.
abstract: BACKGROUND
  Reducing exposure to environmental agents indoors shown to increase asthma symptoms or lead to asthma exacerbations is an important component of a strategy to manage asthma for individuals. Numerous investigations have demonstrated that portable air cleaning devices can reduce concentrations of asthma triggers in indoor air; however, their benefits for breathing problems have not always been reproducible. The potential exposure benefits of whole house high efficiency in-duct air cleaners for sensitive subpopulations have yet to be evaluated.
  
  
  METHODS
  We used an indoor air quality modeling system (CONTAM) developed by NIST to examine peak and time-integrated concentrations of common asthma triggers present in indoor air over a year as a function of natural ventilation, portable air cleaners, and forced air ventilation equipped with conventional and high efficiency filtration systems. Emission rates for asthma triggers were based on experimental studies published in the scientific literature.
  
  
  RESULTS
  Forced air systems with high efficiency filtration were found to provide the best control of asthma triggers: 30-55% lower cat allergen levels, 90-99% lower risk of respiratory infection through the inhalation route of exposure, 90-98% lower environmental tobacco smoke (ETS) levels, and 50-75% lower fungal spore levels than the other ventilation/filtration systems considered. These results indicate that the use of high efficiency in-duct air cleaners provide an effective means of controlling allergen levels not only in a single room, like a portable air cleaner, but the whole house.
  
  
  CONCLUSIONS
  These findings are useful for evaluating potential benefits of high efficiency in-duct filtration systems for controlling exposure to asthma triggers indoors and for the design of trials of environmental interventions intended to evaluate their utility in practice.
authors.affiliation: Environmental Health & Engineering, Inc., 117 Fourth Avenue, Needham, MA 02494-2725, USA. tmyatt@eheinc.com
authors.forename: Theodore A
authors.initials: TA
authors.lastname: Myatt
authors.forename: Taeko
authors.initials: T
authors.lastname: Minegishi
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Allen
authors.forename: David L
authors.initials: DL
authors.lastname: Macintosh
mesh_terms: D000389:Air Conditioning; D016902:Air Pollution, Indoor / Q000009:adverse effects / Q000032:analysis / Q000517:prevention & control*; D000485:Allergens / Q000032:analysis* / Q000276:immunology; D000818:Animals; D001249:Asthma / Q000209:etiology / Q000276:immunology / Q000517:prevention & control*; D002415:Cats; D004781:Environmental Exposure / Q000009:adverse effects / Q000517:prevention & control; D004784:Environmental Monitoring; D005374:Filtration; D006801:Humans; D009975:Orthomyxoviridae / Q000302:isolation & purification; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis; D012229:Rhinovirus / Q000302:isolation & purification; D013172:Spores, Fungal / Q000302:isolation & purification; D014028:Tobacco Smoke Pollution / Q000009:adverse effects / Q000032:analysis; D014691:Ventilation
chemical_list: D000485:Allergens; D052638:Particulate Matter; D014028:Tobacco Smoke Pollution