In Group R-2, R-3, and R-4 occupancies, how many hours is continuous outdoor air ventilation not required?

In Group R-2, R-3, and R-4 occupancies, continuous outdoor air ventilation is not required for a duration of 1 hour. This aligns with certain code provisions that allow for a grace period in buildings where short-term occupancy or infrequent use is anticipated. This leniency ensures that systems can still operate effectively without necessitating continuous fresh air input for brief intervals, allowing for more efficient control of ventilation and helping to optimize energy consumption during those times.

The rationale behind this provision is to balance the need for adequate indoor air quality with the practicalities of system performance and energy efficiency. In the context of such occupancy types, which include residential and multifamily buildings, the code recognizes that immediate and constant ventilation might not be critically necessary at all times, especially during small durations of occupancy.

Understanding this aspect of the code is essential for ensuring compliance and for making informed decisions about HVAC design and operation in residential settings.