Chi Blocking is initially seen being using by Ty Lee as an exclusive ability learned alongside her acrobatic stunts. Ty Lee uses this primarily against Team Avatar to protect herself, a non-bender, against those who bend. She is seen disabling Katara's waterbending on numerous accounts, noticably scaring Katara after her temporary failure to bend. Ty Lee also uses this against Toph and Sokka when Team Avatar challenges Azula.
Ty Lee also used this tactic on Ember Island when Azula challenges Mai. Mai refused to follow Azula's orders, to kill her boyfriend, Zuko, so Azula prepared to challenge Mai. Just before Azula strikes Mai, Ty disables her fire bending and is imprisoned for doing so.
While in prison, Ty Lee teaches old nemesis but now ally, the Kyoshi Warriors, how to use Chi Blocking. The Kyoshi Warriors, though never having demonstrated this ability, may posess the ability to do so.
During the time of The Legend of Korra, the Equalists have now acquired the ability to Chi Block and use it in order to prevent who they think are opressing them, benders. The equalists have adapted new technology in the time of The Legend of Korra and are able to utilize the advances in technology to grant anyone the ability to block a benders chi. This is done using weapons designed specifically by the equalists.