TO EACH ITS BLOW
Whales are mammals and so they have lungs. All couple of minutes, these animals will have to breach the surface of the ocean to take several deep breaths. With each breath, whales replace up to 90% of the air in their lungs - we humans only just exchange 10-15% each time we breathe.
A blue whale's lungs for example hold up to 5000 litres, meaning it might exchange up to 4500 litres per breath. Then, it'll just take 1 to 2 seconds to breathe in again and fill up the lungs.
Being able to conduct long dives afterwards is not only thanks to the lungs' size and the amount of air inside, but mostly due the ability of being able to store oxygen in the red blood cells.
When exhaling, the air is expelled at high speeds - at up to 600km/h in case of the blue whale!
The air leaves the lungs through their nostrils, the so-called blowholes, which are situated on top of their heads.
Whales have a similar body temperature as us humans, of about 37°C. The equally warm air in their lungs condenses upon contact with the colder outside air and forms a white cloud of mist:
The temperature change triggers water vapor in the whale's breath to condense into water droplets - the same phenomenon as happens to us when we exhale on a cold day while the air surrounding us is damp.
The whale's blow though appears even stronger as the air exhaled is compressed. This difference in pressure between the lungs and the surrounding air on the surface causes condensation and vapour.
The pressure with which the whale exhales ensures that no seawater is running into the nostrils and on into the lungs. After every breath, strong muscles - like flaps - close the blow holes tight and seal it.
But what's in a blow?
Apart from moist air, the whale also exhales mucus and bacteria (in fact, the breathing is better compared to our sneezing) as well as seawater and oil droplets from the upper respiratory tract and the top of the blowholes.