Tretagni (त्रेताग्निः)

All Srauta yagnas or yaagas are associated with त्रेताज्ञयः the three Agni's. However, not all three fires are lighted and maintained at all times. त्रेताज्ञयः the three fires are kindled in performance of yaagas. Somayaagas require the kindling of all three fires whereas others do not require so.

A few important features of the three agnis are summarized below

गार्हपत्याग्निः ॥ Gaarhapatya Agni

Information about of गार्हपत्याग्निः ॥ Gaarhapatya agni

• It is used by grihastas for general domestic usage, to cook food and aahutidravyas used in other yagnas by reciting mantras.
• It is placed to the west of the yagnavedi and placed in circular shaped kunda.
• It is ceremonially established with the elaborate vedic procedure involving recitation of specific mantras and is called Agnyādhāna.
• It is rekindled by a special process called "Punaradhana" if it gets extinguished for any reason.
• It is used in nityakarmas.
• It is the only Agni that is maintained continuously and daily aahutis are to be made to this Agni by a grihastha.
• It is the source of other two Agnis
• It is kindled after marriage and and is be worshipped for the rest of the life by the grihastha.
• Only a sapatnika yajamani (grihastha) of the three varnas is allowed to tend the Agnihotram.

आहवनीयाग्निः ॥ Aahvaniya Agni

Some salient aspects about आहवनीयाग्निः ॥ Aahvaniya Agni are as follows

• It is invoked only in special aabhicharika yaagas unlike Gaarhapatya agni.
• The first Aahvaniya agni is established from the Gaarhapatya agni along with the recitation of specific mantras.
• It is not maintained everyday and is considered as Laukikagni at the end of the specific yaaga for which it is invoked.
• It is placed to the east of the yagnavedi, in a rectangular shaped kunda.
• It is used to offer aahutis to the devatas only.

दक्षिणाग्निः ॥ Dakshinaagni

Salient aspects about दक्षिणाग्निः ॥ Dakshinaagni is as follows

• It is invoked only in special yaagas similar to Aahvaniya agni.
• The first Dakshinaagni is established from the Gaarhapatya agni along with the recitation of specific mantras during yagna karmas.
• It is not maintained everyday and is considered as Laukikagni at the end of the specific yaagam for which it is invoked.
• It is placed to the south of the yagnavedi, in a half circle shaped kunda.
• It is used to offer aahutis to the pitrudevatas or forefathers only.

Shatapata Brahmana (11.8.2) mentions about four different fires and their association to the 4 directions.

११.८.२ अग्नेश्चातुर्विध्याभिधायकं ब्राह्मणम्

चत्वारो ह वा अग्नयः। आहित उद्धृतः प्रहृतो विहृतोऽयमेव लोक आहितोऽन्तरिक्षलोक उद्धृतो द्यौष्प्रहृतो दिशो विहृतोऽग्निरेवाहितो वायुरुद्धृत आदित्यः प्रहृतश्चन्द्रमा विहृतो गार्हपत्य एवाहित आहवनीय उद्धृतोऽथ यमेतमाहवनीयात्प्राञ्चं प्रणयन्ति स प्रहृतोऽथ यमेतमुदञ्चम्पशुश्रपणायाहरन्ति यं चोपयङ्भ्यः स विहृतस्तस्मात्प्रहार्येऽग्नौ पशुबन्धेन यजेत - ११.८.२.[१]