Generally, kelnorim is a replacement for sleep -- which Jaffa do not do.
Holiday - Colonel O'Neill experiences kelnorim when his consciousness is transferred into Teal'c's body, which has contracted an illness.
Demons - Teal'c survives an attempted execution by drowning by entering a state of kelnorim, allowing his larval symbiote to sustain his body.
Beneath the Surface - His memory blocked by alien technology, Teal'c falls dangerously ill when he does not know his body requires kelnorim.
Tangent - Trapped in a Goa'uld death glider heading into deep space, Teal'c initiates Kelnorim to conserve oxygen.
Orpheus - Teal'c teaches Daniel kelnorim meditation, in the hopes that it will help him recover his lost memories.