Table 1.

Setup of the experiment to determine the PM load and thermal microclimate in a university classroom in the presence of various groups of students without masks (2019) and with disposable face masks (2021).

Indicator	Descriptor
Location	Valahia University Campus, Targoviste, Romania—Classroom A227
Study period	3 h monitoring for each group in different days of March 2019 and in March 2021 (with anti-COVID protection measures)
Groups of students	2019—2 groups A (n = 17)—age (18–38); 13 females and 4 males. B (n = 17)—age (19–38); 14 females and 3 males. 2021—2 groups C (n = 9)—age (19–30); 9 females. D (n = 9)—age (19–43); 7 females and 2 males. Total = 52 students + 1 professor which was present in all groups (male)
Fields in the observation sheet completed by each student	age; weight; height; medication during the trial; presence of respiratory symptoms; physical effort before entering in the classroom; body temperature before entering the classroom.
Classroom	Surface (m2) = 50; Height (m) = 3; Volume (m3) = 150; Volume per person (m3/person) A-8.33 B-8.33 C-15 D-15 Nominal occupancy (person/m2) A-0.36 B-0.36 C-0.2 D-0.2
Respiratory characteristics	VE—minute ventilation (the total volume of gas entering or leaving the lungs per minute-L/min). VE = VT × f (where VT—tidal volume; f—respiratory rate). AVE—alveolar minute ventilation (L/min); AVE = VE − VD (where VD—physiological dead space); VD = 1 mL/pound IBW (where 1 pound = 0.45359237 kg; IBW—ideal body weight) IBW estimated using the formula of Devine (1974) https://www.calculator.net/ideal-weight-calculator.html, accessed on 5 June 2021 VT = 5–7 mL/kg f1 = 10–11 breathes/min considering a sedentary activity without mask f2 = 12–14 breathes/min considering a sedentary activity wearing mask