As per yoga tantra when we breathe only one of our nostrils is active.
When hot air is blowing through the nostrils exuberantly then Surya nadi is active during which hot mantras should be chanted.
Hot mantras are known as Agneya in Sanskrit language which are used for destruction purposes.
When cold air is blowing through
the nostrils exuberantly then Chander nadi is active during which cold mantras should be chanted which are known as Saumya in
Sanskrit language. Saumya mantras are used for good purposes.