3 sentences

1. 听到火警后，所有人立即撤离。

   tīng​dào huǒ​jǐng hòu, suǒ​yǒu rén lì​jí chè​lí.

   Upon hearing the fire alarm, everyone evacuated immediately.

   Source: Dong Chinese Dictionary

2. 打电话报火警。

   dǎ diàn​huà bào huǒ​jǐng.

   Call the fire department.

   Source: OpenSubtitles

3. 火警铃响后，大楼内的人员开始有序地疏散。

   huǒ​jǐng líng xiǎng hòu, dà​lóu nèi de rén​yuán kāi​shǐ yǒu​xù de shū​sàn.

   After the fire alarm rang, people in the building began to evacuate in an orderly manner.

   Source: Dong Chinese Dictionary