4 sentences

1. 你一定松一口气了。

   nǐ yī​dìng sōng yī​kǒu​qì le.

   You must be relieved.

   Source: OpenSubtitles

2. 他找到钱包时松了一口气。

   tā zhǎo dào qián​bāo shí sōng le yī​kǒu​qì.

   He heaved a sigh of relief when he found his wallet.

   Source: UM-Corpus: Spoken

3. 看着救护车远去，工作人员终于松了一口气。

   kàn zhe jiù​hù​chē yuǎn qù, gōng​zuò​rén​yuán zhōng​yú sōng le yī​kǒu​qì.

   Watching the ambulance go away, the staff finally breathed a sigh of relief.

   Source: CCMatrix

4. 当他接电话时，听上去松了一口气，因为我终于打了电话。

   dāng tā jiē diàn​huà shí, tīng shàng qu sōng le yī​kǒu​qì, yīn​wèi wǒ zhōng​yú dǎ le diàn​huà.

   When he answered the phone, he sounded relieved that I had finally called.

   Source: CCMatrix