title: Gas-phase photolytic production of hydroxyl radicals in an ultraviolet purifier for air and surfaces.
abstract: We have measured the concentration of hydroxyl radicals (OH) produced in the gas phase by a commercially available purifier for air and surfaces, using the time rate of decay of n-heptane added to an environmental chamber. The hydroxyl generator, an Odorox® BOSS™ model, produces the OH through 185-nm photolysis of ambient water vapor. The steady-state concentration of OH produced in the 120 m3chamber is, with 2σ error bars, (3.25 ± 0.80) × 106cm-3. The properties of the hydroxyl generator, in particular the output of the ultraviolet lamps and the air throughput, together with an estimation of the water concentration, were used to predict the amount of OH produced by the device, with no fitted parameters. To relate this calculation to a steady-state concentration, we must estimate the OH loss rate within the chamber owing to reaction with the n-heptane and the 7 ppb of background hydrocarbons that are present. The result is a predicted steady-state concentration in excellent agreement with the measured value. This shows we understand well the processes occurring in the gas phase during operation of this hydroxyl radical purifier.
  
  
  
  Hydroxyl radical air purifiers are used for cleaning both gaseous contaminants, such as volatile organic compounds (VOCs) or hazardous gases, and biological pathogens, both airborne and on surfaces. This is the first chemical kinetic study of such a purifier that creates gas-phase OH by ultraviolet light photolysis of H2O. It shows that the amount of hydroxyls produced agrees well with nonparameterized calculations using the purifier lamp output and device airflow. These results can be used for designing appropriate remediation strategies.
authors.affiliation: a Private consultant to HGI Industries (Boynton Beach, Florida) , Palo Alto , CA , USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Crosley
authors.affiliation: b Prometheus Strategies , Delray Beach , FL , USA.
authors.forename: Connie J
authors.initials: CJ
authors.lastname: Araps
authors.affiliation: c Lovelace Respiratory Research Institute , Albuquerque , NM , USA.
authors.forename: Melanie
authors.initials: M
authors.lastname: Doyle-Eisele
authors.affiliation: c Lovelace Respiratory Research Institute , Albuquerque , NM , USA.
authors.forename: Jacob D
authors.initials: JD
authors.lastname: McDonald
mesh_terms: D006536:Heptanes / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D010126:Ozone / Q000737:chemistry; D010782:Photolysis; D014466:Ultraviolet Rays; D055549:Volatile Organic Compounds
chemical_list: D006536:Heptanes; D055549:Volatile Organic Compounds; D017665:Hydroxyl Radical; C028618:n-heptane; D010126:Ozone