In order to get an idea of the various chemical changes which take place, it is essential to know the various substances offered in Yagya.
(A) Wood: Wood has to be dry and free from dust, insects and worms. The wood is cut into small sticks of varying lengths called Samidhas according to the size of the altar or Agnikunda.
The principal types of wood used are the following:-
I. Sandal-wood (Santalum Album)
II. Agar and Tagar wood (Aquilana Malaccensis and Valeriana Wallchii)
III. Deodar (Cedrys Libani)
IV. Mango (Mangifera Indica)
V. Dhak or Palash (Butea Frondosa)
VI. Bilva (Aegle Marmelos)
VII. Pipal (Ficus Religiosa)
VIII. Bargad (Ficus Bengalensis)
IX. Shami (Proposis Spicigera)
X. Gular (Ficus Glomerata)
In addition to wood, various Havishya or Havan samagri are offered in Yagya
can be divided into the following four groups:
(B) Odoriferous Substances:-
These are - saffron, musk, agar, tagar, chandan, illaychi, jayphal, javitri and camphor.
(C) Substances with Healthy Constituents:-
These are clarified butter (ghee), milk, fruits and cereals like wheat, rice, barley, til, kangu, munga, chana, arhar, masur or peas.
(D) Sweet Substances:-
These usually are - sugar, dried grapes, honey or chhuhara.
(E) Medicinal Herbs:-
These are used as per specific requirement. Some common herbs are
Somalata or Giloya, Brahmi, Shankhpushpi, Nagkesar, Mulhati,Red Chandan, Baheda, Sonth and Harad.
Now-a-days Havan -samagri is readily available in the market consisting of the following substances in a crude powder form: Saw dust of sandal-wood and pine wood, the agar and tagar wood chips, kapurkachari, gugal, nagarmotha, balchhaar or jatamansi,narkachura, sugandhbala, illayachi, jayphal, cloves and dalchini.