The new National Children's Hospital has been ordered to install a more extensive sprinkler system.
The hospital had appealed against the condition imposed by the Fire Brigade but An Bord Pleanála ruled that sprinklers must be fitted throughout the building.
It said that, given the design, it would limit the size of any fire and provide extra time to escape.
An Bord Pleanála also imposed a new condition that if Christmas trees are to be installed in the atrium they must be artificial, fire retardant and a maximum height of 2.5 metres.
It removed two other conditions that the hospital had appealed against but said if there were any design changes to the atrium a new fire safety certificate would be required.