The ventilation rates provided in the code are based on the absence of which of the following in occupiable spaces?

The ventilation rates detailed in the International Mechanical Code (IMC) are formulated with the assumption that certain activities or elements, such as smoking, are not present in occupiable spaces. This is important because smoking can significantly increase the levels of indoor air pollutants, necessitating higher ventilation rates to maintain acceptable air quality.

When smoking is absent, the baseline ventilation rates are designed to effectively manage typical contaminants generated from activities such as occupancy, office equipment, or low levels of housekeeping activities. The code aims to ensure adequate air exchange for these more predictable sources of pollution. By setting these rates under the assumption that more harmful activities like smoking do not occur, the code provides a standard that is manageable and practical for general conditions in occupiable spaces.

In contrast, food preparation, heating appliances, and dust and pollutants may still be present in normal situations, but they do not fundamentally alter the standard ventilation needs defined for healthy indoor environments as significantly as smoking does.