OSHA recommends that employers encourage workers to wear cloth face coverings at work to help reduce the spread of COVID-19 and give guidance when workers who wear cloth face coverings in hot and humid environments or while performing strenuous activities indoors find cloth face coverings to be uncomfortable.

Read entire article (pdf) - https://www.osha.gov/SLTC/heatstress/covid-19-cloth-coverings-indoor-heat.pdf