In News and Media: Journalists often use it to describe accidents, daring rescues, or political crises. For example, a report on firefighters pulling someone from a burning building might describe the rescue as happening at the 千钧一发 moment.
In Storytelling: It's a staple in movies, TV shows, and novels to build suspense. The hero defusing the bomb with one second left is a classic 千钧一发 scene.
In Conversation: While less common in casual daily chat, people might use it to recount a serious, life-threatening experience, like narrowly avoiding a major car accident. It is almost always used to describe a dangerous situation that was, thankfully, averted.
Common Structure: It is often used with 之际 (zhī jì), meaning “at the moment of…”. For example, 在千钧一发之际 (zài qiān jūn yī fà zhī jì) translates to “at the critical, hair's-breadth moment.”