Summary: Shiva and Shakti symbolize life, life-force, dynamism, consciousness, intelligence, senses, breath, the life-energy (prana) that flows in the nadis, and the Shaktis who rule the organs in the body in all the four states in both ignorant and enlightened beings. When they are present the body is auspicious (Shiva). When they depart, the body becomes inauspicious (shava)..
Siva means the auspicious. That auspicious quality comes from his being present in the macrocosm as well as in the microcosm as the purifier, liberator and sustainer. By His mere presence, the world comes to life and so also the body.
The body is pure as long as He is present in the body and when He departs it becomes impure. He is also the lord of the breath. As the lord of the breath (prana nath or pranesvar) and its source, He symbolizes the breathing body and all that breathes in creation.
In the Upanishads, the breath is declared as the lord of the body. In the development of Vedic belief system, breath was originally equated with the Self (atman). The very meaning of Atman means the breathing one.
In the body, breath is considered superior to the other organs becaue it cannot be brought under the sway of desire. Whether you like it or not you have to breath. Hence, breath is considered a purifier and destroyer of evil and other bodily impurities.
Breath also plays an important role in restraining the mind and the senses. Since, breath is a controller, auspicious, and life sustaining, it is equated with the Siva (self) in the body.
All is Siva. That is the motto of a devotee who sees Him everywhere and in everything and everything in himself. A breathing body is Siva. It is pure and auspicious.
A body without breath is sava, a dead body. It is impure and inauspicious. Hence, people invariably take a bath if they touch a dead body or when they carry it to the cremation grounds.
Lord Siva is also Omkaresvar. Aum is known as pranava, because it is deeply connected with breath and represents the sound of breath. As long as a person is alive and keeps breathing, he chants Aum continuously, without even knowing it.
When you become aware of the sound of Aum in your breathing and concentrate upon it continuously without any distraction, with that sound you will eventually overcome your delusion, egoism and bondage and achieve liberation.
You may check these links also.
Agamas, The Sacred Literature Of Saivism
Aspects and Manifestations Of Lord Siva
Bataraguru Or Divine Teacher - Siva In Malay Tradition
The Churning Of The Ocean - A Hindu Legend From Purana
The Dharma Of A Householder On The Path To Salvation
The Story Of The Great God Siva Or Mahadev
Maya, The Illusion or The Delusion Of The Embodied Soul
Symbolism of Nataraja, The Lord Of The Universal Dance
Pasa, the Impurities of Anava, Karma and Maya in Saivism
Pasu The Deluded Soul Caught In Animal Nature
Pati the Lord of Creation in Saivism
Shakti, the Dynamic Energy of Siva
Symbolism of Siva As the Breathing Body and Prana
The Symbolism and Worship of Sivalingas in Saivism
The 36 Tattvas and Their Significance
Siva--Ideal of Manhood, Embodiment of Godhead
How To Worship Lord Shiva or Siva and Shivalingam
The Growth of Hinduism From Vedic Religion
The History Of Shaivism In Southern India
A History of Shiva and Vishnu Worship
Ganesha Symbolism and Significance
Aspects of Shakti, The Mother Goddess