CO↓2 gun

例句：

1. 1. The CO2 gun is used to test the air quality in a room.
   二氧化碳枪用于测试房间的空气质量。
2. 2.The CO2 gun was used to clear the smoke from the room.
   二氧化碳枪被用来清除房间的烟雾。
3. 3. The CO2 gun was used to measure the concentration of CO2 in the air.
   二氧化碳枪被用来测量空气中二氧化碳的浓度。