A Chandi Homa performed with authenticity for those curious on how exactly it is done.
The period this was done is called Varahi Navaratri (nine nights dedicated to the goddess named Varahi, who represents the physical energy of the Goddess and is invoked to protect oneself from dangers) - and hence her seed mantra is used to sandwich every verse of Saptashati 700 verses (called samputa or sandwiching technique) - which generates a very unique and powerful effect that is a combination of two deities - Chandi and Varahi.
The fire ritual is empowered by these aspects - breath control, mantra, intention, an existing connection to the deity by the main conductor of the ritual, presence of mandalas/yantras to focus the energy and finally, fire consecrated through mandalas and mantras which amplifies the energy and brings through the presence of the deity invoked. The ritual is generally preceded by a million recitations of the mantra, and followed by feeding the poor, charity, etc.