The IBC-2000 and 2003 primarily addressed critical equipment being certified to be able to withstand certain seismic design loads of a given project. Critical equipment needs to be certified through independent analysis or testing to prove the equipment will remain operational after a seismic event. The 2006 version of the code does not limit the online functionality of critical equipment to only seismic events. It implies equipment should remain operational after other natural events such as wind.

The U.S. Geological Survey (USGS) also changed some of the values of the mapped short period response spectra (Ss) throughout the country. In some areas some values went up in others they went down.

The biggest changes to the code occurred in the 2006 version where factors such as the Response Modification Factor (Rp) and Amplification Factor (ap) changed. This has caused the calculation for the seismic design force to increase dramatically for engine generator sets.