2020 No https://www.tandfonline.com/doi/full/10.1080/15459624.2020.1776300 Ierardi, A. Michael North America Observational Epidemiology Study Staff Elementary (K-5) Middle/Jr High (6-8) High School (9-12) Temperature Carbon Dioxide (CO2) Carbon Monoxide (CO) Chef Cook Heat-related illness Heat-related injury Thermal stress The overall mean indoor WBGT index for all ten sites was approximately 25.0 C (77.0 F; Standard Deviation SD]¼2.0 C). Regarding the estimated Action Limit, 10% of school kitchens sampled exceeded this recommended limit for the light work-rate scenario; 60% of schools exceeded this limit for the moderate work-rate scenario; and 80% of schools exceeded this limit for the heavy work-rate scenario. For the Threshold Limit Value (TLV), none of the kitchens exceeded this limit for the light or moderate work-rate scenarios; 30% of kitchens were in excess of this limit for the heavy work-rate scenario. Mean full-shift CO2 and CO air concentrations ranged from 435–911 ppm (mean ¼ 648; SD ¼ 158) and 0.0–3.2ppm (mean ¼ 0.9; SD ¼ 0.9), respectively.