Which standard provides guidelines specifying thermal conditions acceptable for occupants in a space?

ASHRAE 55 is the standard that outlines the parameters for acceptable thermal conditions for occupants in indoor environments. This standard emphasizes the importance of thermal comfort, defining the environmental factors—such as air temperature, humidity, and air velocity—that contribute to a comfortable space for individuals. It also addresses the variation in body heat and activity levels among occupants, which is critical for achieving comfort in diverse settings.

In contrast, ISO 7708 pertains to air quality and does not specifically focus on thermal conditions. ASHRAE HVAC Handbook provides comprehensive information related to heating, ventilation, and air conditioning systems but doesn't provide targeted guidelines for thermal comfort in the same way that ASHRAE 55 does. ISO 7730 also deals with thermal comfort but is not as widely recognized or utilized as ASHRAE 55 within the context of U.S. building standards. Hence, ASHRAE 55 establishes the benchmark for thermal comfort standards, making it the correct choice for this question.