Some of the significant changes that are found in the 2009 codes include:

• Carbon monoxide detectors will be required in residential occupancies.  Existing dwelling units, other than owner-occupied single family residences, will be required to comply beginning in July 2011.
• A “flow-through” residential sprinkler design method has been added to the Residential Code.  It’s a lower cost method that uses the building’s plumbing system for sprinklers.  (Sprinklers are optional under the Seattle Residential Code.)
• New provisions governing ambulatory health care are added to the Building Code.
• Areas of refuge for persons with impaired mobility will not be required in sprinklered buildings.
• Several new provisions apply to high-rise buildings:
  • Luminous egress path marking will be required in Groups A, B, E, I, M and R-1
  • Seattle will allow elevator lobbies as an alternative to hoistway pressurization.
  • Buildings more than 120 feet in height will be required to have fire service access elevators with enhanced features to aid firefighters.
  • Buildings more than 420 feet in height will be required to have either one additional exit stairway or occupant evacuation elevators.  The elevators would be available for building occupants when there is an alarm in the building before the elevators are recalled to the main floor.
• A provision allowing reduced width for means of egress in sprinklered buildings has been deleted from the IBC. Seattle is proposing an amendment that would allow the reduced width in most sprinklered high-rise buildings.
• The State Ventilation and Indoor Air Quality Code has been rescinded, and its provisions are being added to the Residential, Building, and Mechanical codes.
• The ventilation provisions of the Mechanical Code are revised to be consistent with a newer edition of ASHRAE’s national ventilation standards.