Hilton Hawaiian Village in Waikiki, one of the world's largest resorts, has closed all 453 guest rooms in the newest of its six towers and is spending $10 million to rid it of a potentially dangerous mold called eurotium.

Hilton opened the $95 million Kalia Tower last year. David Odom of CH2M Hill said that his team, which has been studying Kalia Tower blueprints as well as findings from Air Quality Sciences' mold investigators, has some ideas about the cause, but not enough to speculate. Identifying the humidity source is difficult, say mold investigation experts, because the problem could be from an architectural or engineering design fualt, construction defect, malfunctioning equipment or any combination. Odom said typical causes of mold in other high-rise hotels have been most often linked to deficient air conditioning systems and air or water penetrating building walls.

"It happens a lot more than you would expect," he said.

Charlie Wiles of the American Indoor Air Quality Council said avoiding air pressure, condensation or water-leak problems in constructing of operating a high-rise hotel is difficult. Typically buildings in humid climates such as Hawaii are designed to be slightly pressurized to keep warm air out.

"In the case of Hawaii, keeping indoor temperature above the dew point may prove to be extremely challenging," he said.