Which body establishes optimal temperature and humidity levels?

The correct answer is indeed the organization that stands for the American Society of Heating, Refrigerating and Air-Conditioning Engineers. ASHRAE is a global society advancing human well-being through sustainable technology for the built environment. This organization develops standards and guidelines for optimal indoor environmental conditions, which include temperature and humidity levels essential for maintaining comfort, health, and energy efficiency.

ASHRAE specifically publishes industry standards that define acceptable ranges for temperature and humidity to ensure the well-being of occupants and the efficient functioning of HVAC systems. Their standards play a crucial role in designing environments like office spaces, educational institutions, and healthcare facilities to achieve energy efficiency while ensuring comfort and health.

The other options, while they may sound similar, do not refer to the correct organization or are not known for establishing these specific standards and guidelines.