Spiritual Meaning:
Spiritually, air signifies the Breath of Life and is the second element in the four creative elements of Fire, Air, Water and Earth, which together are part of the manifestation.

Psychological / Emotional Perspective:
Air represents the intellect and psychologically allows us to bridge the gap between the spiritual realm and the physical. As breath, it is a necessary part of life which tends not to be thought about until there is a problem. In dreams we will become conscious of air as a breeze or a wind of some sort.

Everyday Material Aspects:
From a pragmatic point of view, air is a force which supports and surrounds all that we do, so in dreams to be conscious of bellows or a pump suggests that we need to use strategy and power to achieve our ends.

Consult the entry for Wind for further clarification.