Thermoregulation and thermal sensation in response to wearing tight-fitting respirators and exercising in hot-and-humid indoor environment. (August 2019)

• Record Type: Journal Article
• Authors: Lin, Yi-Chun; Chen, Chen-Peng
• Is Part Of: Building and environment. Volume 160(2019)
• Publication Date: 2019-08
• Subjects: Thermo-physiology -- Thermal sensation vote -- Acclimatization -- Respirators -- Thermal microclimate -- Metabolic heat; Buildings -- Environmental engineering -- Periodicals; Building -- Research -- Periodicals; Constructions -- Technique de l'environnement -- Périodiques; Electronic journals; 696
• DOI: 10.1016/j.buildenv.2019.05.036
• Languages: English
• ISSNs: 0360-1323

Abstract

Abstract: Half-mask respirators have been increasingly used in public facilities to protect against indoor air contaminants. However, when they are used, the respiratory heat flow is restrained and its release into the environment is limited. This study evaluated the thermal burden on respirator users in an indoor environment where a significant heat load from hot-and-humid air is introduced. Twenty-five participants walked on the stairs at a speed of 4.6 km/h wearing a filtering facepiece respirator (N95 mask) or elastomeric facepiece respirator under varying air temperatures and relative humidity (RH). The thermo-physiological properties on the nasal, facial, and forearm skin and the temperature/RH of the breath were evaluated. Thermal sensation was also surveyed. The results showed that a thermal microclimate was developed inside the mask, with the heat index in the microclimate of N95 masks being elevated to 61.2–67.9 °C and a risk level of "Extreme Danger". The metabolic heat from respirator use shifted the paradigm of thermoregulation to a scheme involving localized enhancement in thermoregulation. When using N95 masks the skin moisture level was increased by 77%–588% and the transepidermal water loss by 18%–72%. Thermoregulation underlying heat strain was near-saturated at 33 °C, and an abrupt increase of 1.6- to 3.6-fold in thermal sensation was concurrently observed. The threshold-controlled increase in sensation was likely a result of the thermal strain capacity being overwhelmed. These findings demonstrated that even under room temperature, caution should be exercised when using N95 masks for performing tasks of moderate metabolic load. Graphical abstract: Image 1 Highlights: Respirators added to thermal stress when used in hot-and-humid environment. Microclimate inside respirators shifted paradigm of metabolic heat release. Thermoregulation plateaued at high temperature and sensation reached the threshold. Filtering facepiece without exhalation valve restricted respiratory heat flows. Caution is warranted when using N95 masks and exercising indoors to reduce stress.