title: Time dependent infrared thermographic evaluation of facemasks.
abstract: BACKGROUND
  Few studies have investigated silent versus speaking situations while wearing various types of facemasks over a period of time.
  
  
  OBJECTIVE
  The main objective of this study is the evaluation of temperature changes with time and the thermal comfort of facemasks under different verbal output conditions.
  
  
  METHODS
  A two-way within-subject experiment was conducted to find the effects of facemask types and verbal output conditions. The infrared thermographic technology was used to record the video during the experiment. A subjective questionnaire was applied to measure the perception ratings of thermal discomfort.
  
  
  RESULTS
  Wearing a facemask could result in a higher face temperature compared to the condition in which a facemask was not worn. The N95 mask created the highest temperature value in the cheeks and nose/mouth regions. The speaking condition did not present significant difference on face temperature compared to the silent condition. Participants tended to provide higher subjective ratings of perceived humidity, heat, breathing difficulty and overall discomfort while wearing facemasks, especially while wearing the N95 mask and during the speaking conditions.
  
  
  CONCLUSIONS
  Facial temperature distribution demonstrated various trends with time under different conditions. Facemask types had significant effects on facial temperature and perceived thermal comfort.
authors.affiliation: School of Design, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: Yan
authors.initials: Y
authors.lastname: Luximon
authors.affiliation: School of Design, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Anne Sheen
authors.affiliation: The Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: Ameersing
authors.initials: A
authors.lastname: Luximon
mesh_terms: D000328:Adult; D005260:Female; D006723:Hong Kong; D006801:Humans; D008297:Male; D008397:Masks / Q000592:standards*; D008875:Middle Aged; D011795:Surveys and Questionnaires; D013817:Thermography / Q000379:methods*; D000071436:Thermotolerance; D014705:Verbal Behavior
keywords: Thermal comfort; subjective perceptions; temperature distribution