There are several significant changes to ASHRAE Standard 62.1 Ventilation for Acceptable Indoor Air Quality between the 2007 version and the newly issued 2010 version including many changes that may impact energy use in buildings. Changes of in procedures include revisions to the IAQ procedure and the additional requirements for natural ventilation systems. The ventilation rate procedure for multiple zone systems (especially VAV systems) is clarified in a rewritten Appendix A. A section of the standard addressing demand control ventilation was added to clarify the circumstances when ventilation during operations can be reduced from the zone design ventilation rates.