A Shiva Linga consists of three parts, the lowest of which is called the 'Brahma-Pitha,' the middle one, the 'Vishnu-Pitha' and the uppermost one, the 'Shiva-Pitha.There is a mysterious or indescribable power or 'Shakti' in the Linga, to induce concentration of the mind, and helps focus one's attention. That is why the ancient sages and seers of India prescribed Linga to be installed in the temples of Lord Shiva.

In Sanskrit, Linga means a 'mark' or a symbol, which points to an inference. Thus the Shiva Linga is a symbol of Lord Shiva - a mark that reminds of the Omnipotent Lord, which is formless.

A Shiva Linga consists of three parts, the lowest of which is called the 'Brahma-Pitha,' the middle one, the 'Vishnu-Pitha' and the uppermost one, the 'Shiva-Pitha.There is a mysterious or indescribable power or 'Shakti' in the Linga, to induce concentration of the mind, and helps focus one's attention. That is why the ancient sages and seers of India prescribed Linga to be installed in the temples of Lord Shiva.

For a sincere devotee, the Linga is not merely a block of stone. It is all-radiant - talks to him, raises him above body-consciousness, and helps to communicate with the Lord. Lord Rama worshiped the Shiva Linga at Rameshwaram. Ravana, the learned scholar, worshiped the golden Linga for its mystical powers.For me, it literally means the body of Shiv. Next to the symbol of Om, it is perhaps the most potent, powerful and popular symbol in the entire Hinduism.

It resembles the male sexual organ, suggestive of the creative power of Shiv. The circular base resembles that of the female, suggestive of his consort Paarvatee. Physically a Shiv Ling is a phallic symbol, representing the male and female sexual organs in a state of conjugal bliss.

In the astrological sense, the base represents the earth's monthly rotation with the Moon. Since Shiv wears the Moon upon his head, the Ling is verily the center around which the Moon moves every lunar month. This very fact makes the lunar Tithi the basis of all our festivals. Since Shiv wears the Moon upon his head we may also say that, in the physical sense, the Ling represents the thalamus at the center of our brain cortex, within our head.

This fact is mentioned in the sense of Purush and Prakriti. Prakriti is the earth and Purush is the center, around which the earth goes every lunar month. This is the astrological or astronomical meaning of the Shiv Ling. Since there are 12 lunar months in one year, we can say that there are 12 Jyotirling in Bhaarat Varsh. Bhaarat "Varsh" is of course earth's one 'year' travel around the Sun.

There are 12 'Jyotir-lingas' and 5 'Pancha-bhuta Lingas' in India. The dozen Jyotir-lingas are: Kedarnath, Kashi Vishwanath, Somnath, Baijnath, Rameswar, Ghrusneswar, Bhimshankar, Mahakal, Mallikarjun, Amaleshwar, Nageshwar and Tryambakeshwar. The 5 Pancha-bhuta Lingas are: Kalahastishwar, Jambukeshwar, Arunachaleshwar, Ekambareshwar of Kanjivaram and Nataraja of Chidambaram. The temple of Lord Mahalinga at Tiruvidaimarudur known also as Madhyarjuna is regarded as the great Shiva temple of South India.

So every person maintains Shiva Linga in his home, should see that his Linga is kept in cold place, and constant cold water should flow over him, not one drop per second, so please keep your Shiva Linga cold and well dipped in cold water or milk. This will help everyone and everything to cool down.. There is not such written fact on why shivaling cant be placed at home.... its a personal decsision eventually,  However.... if you choose to keep.... you have to take utmost care apart from basic hygiene and pooja. especially of following things... Pray Daily Use only ice cold milk, no packets stuff No Coconut water... coconut is fine The shivling should be first offered Panchamrit. Never offer kewda and champa flowers as they are said to be cursed by Lord Shiva. If the shivling is worshipped without the jaldhara it attracts negative energies.