title: Minimal heating dose: a novel biological unit to measure infrared irradiation.
abstract: OBJECTIVE
  Infrared (IR) rays, which comprise approximately 40% of the solar radiation which reaches the earth's surface, have received relatively scant attention. As no standard method has yet been agreed upon for the biological evaluation of IR irradiation, the objective of this study is to suggest a new unit for IR irradiation.
  
  
  METHODS
  The skin temperature of 38 Korean volunteers was measured after IR irradiation with varying irradiance.
  
  
  RESULTS
  Skin temperature after IR irradiation at an irradiance of 2.02 W/cm2 remained unchanged after 652+/-22 s (mean+/-standard error), which corresponds, in this case, to a total radiation dose of IR 1317.3+/-44.84 J/cm2. This quantity was designated as the minimal heating dose (MHD). We also demonstrated that MHD increased with increasing IR irradiance at lower IR irradiance (1.17 and 2.02 W/cm2), whereas it became constant at higher irradiance (2.87 and 3.22 W/cm2). No statistically significant correlations were detected between MHD and volunteers' ages, erythema index, or melanin index.
  
  
  CONCLUSIONS
  We propose 'MHD' as a biological unit for the measurement of IR irradiation.
authors.affiliation: Department of Dermatology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Hyoun Seung
authors.initials: HS
authors.lastname: Lee
authors.forename: Dong Hun
authors.initials: DH
authors.lastname: Lee
authors.forename: Soyun
authors.initials: S
authors.lastname: Cho
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Chung
mesh_terms: D000328:Adult; D044466:Asian People; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D007259:Infrared Rays; D007723:Korea; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D012107:Research Design / Q000592:standards; D012882:Skin Tests / Q000379:methods