The World Health Organization in 1987 found that comfortable indoor temperatures of between  were not associated with health risks for healthy adults with appropriate clothing, humidity, and other factors. For infants, elderly, and those with significant health problems, a minimum  was recommended. Temperatures lower than  with humidity above 65% were associated with respiratory hazards including allergies.
The WHO's 2018 guidelines give a strong recommendation that a minimum of  is a "safe and well-balanced indoor temperature to protect the health of general populations during cold seasons". A higher minimum temperature may be necessary for vulnerable groups including children, the elderly, and people with cardiorespiratory disease and other chronic illnesses. However, the recommendation regarding risk of exposure to high indoor temperatures is only "conditional". Minimal-risk high temperatures range from about  depending on the region, with maximum acceptable temperatures between .