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Blue Lum
Blue Lums contain the first breath. They are the origin of all life. Each creature receives at birth his Blue Lums and keeps them until the day they die.
Blue Lums are a type of Lum which appears in Rayman 2, the Game Boy Advance version of Rayman 3, the mobile phone version of Rayman 3, Rayman: Hoodlums' Revenge and the Game Boy Advance version of Rayman Raving Rabbids.
In Rayman 2
Oxygen rich, they restore Rayman's Air Gauge when he's moving under water.—Manual, Rayman 2

In all versions of Rayman 2 except for Rayman Revolution in which they are replaced with air bubbles, Blue Lums can be found underwater. They contain oxygen, which Rayman needs when he swims in bodies of water he cannot resurface to, otherwise his oxygen meter will run out and he will drown. Some stay and provide an unlimited amount of oxygen while others disappear for a while once they have been collected.
Blue Lums in Rayman 2 are said to represent the origin of all life, and the very first breath of a creature's life. When a creature is born, it is given Blue Lums to keep until the day it dies. As he is the only being Polokus did not dream, Rayman may or may not carry his own Blue Lums in this way.
In the Game Boy Advance version of Rayman 3, the mobile phone version of Rayman 3 and the Game Boy Advance version of Rayman Raving Rabbids
These enable Rayman to prolong the helicopter.

In the Game Boy Advance version of Rayman 3, the mobile phone version of Rayman 3 and the Game Boy Advance version of Rayman Raving Rabbids, Blue Lums resemble Tings and do not give Rayman air; instead they briefly grant him the super helicopter power, much like the potion he receives from the Musician in the original Rayman game. The smaller variant has a timer on the super helicopter power, while the bigger once, known as Super Blue Lums, lasts the entire level. In the Game Boy Advance version of Rayman 3, Rayman can first use them once Ly gives him the ability to do so in the level River of Fire.
A Blue Lum in the Game Boy Advance version of Rayman 3.
A Blue Lum in the Game Boy Advance version of Rayman Raving Rabbids.
In Rayman: Hoodlums' Revenge
—Manual, Rayman: Hoodlums' Revenge
In Rayman: Hoodlums' Revenge, Blue Lums act as fuel which sustains the Throttle Copter – a separate pick-up which allows Rayman to fly via a mechanical apparatus attached to his head. Rayman must quickly collect Blue Lums in order to keep the Throttle Copter from running out.