Pulmonary edema occurs when the alveoli fill up with excess fluid seeped out of the blood vessels in the lung instead of air. This can cause problems with the exchange of gas (oxygen and carbon dioxide), resulting in breathing difficulty and poor oxygenation of blood.
Currently buildings are limited to a height of 200 meters and are subject to not contrasting the view of Mount Royal, the city's central green space, with the only exception being antennas and communication towers, that are allowed to reach 223 metres (732 ft) above mean sea level.
Newer buildings tend to be larger than older buildings. The average size of buildings constructed before 1960 (26% of the commercial building stock) is 12,000 square feet; buildings constructed between 1960 and 1999 (55%) average 16,300 square feet; and buildings constructed in the 2000s (18%) average 19,000 square feet.