When the temperature drops below 0°C, users can add an appropriate amount of antifreeze to the cooling water or draw off the water to prevent the cooling water of the CO₂ laser tube from freezing. Users shall pay attention when using antifreeze:

1. Users shall choose an antifreeze with good fluidity, strong antifreeze ability, low volatility, weak corrosivity and good heat dissipation. In order to avoid freezing and cracking of the laser tubes, the freezing point of the antifreeze shall be 5℃ lower than the lowest temperature of the actual operating environment.
2. Generally, higher concentration of antifreeze means worse fluidity and heat dissipation effect. Users shall choose antifreeze according to the actual use situation and be careful when using it. Common antifreezes in the market are generally made of ethylene glycol and water. The relationships between ethylene glycol concentration and the antifreeze ability are shown as follows:

1. When adding antifreeze, users shall pay attention to the changes in the cutting speed and laser beam quality before and after the replacement. Slower cutting speed, abnormal cutting process, or abnormal laser spot after the replacement of antifreeze means that the antifreeze has impacted the output power and laser beam quality. In such cases, users need to replace the antifreeze of other brands or types.
2. When the temperature rises above 0°C, the antifreeze in chillers, tubes and pipes shall be drawn off and replaced by water in time. If the antifreeze in the water circulation system of the laser equipment is not fully drawn off, users can repeat the process of adding water into chiller and drawing off the water for several times to prevent dirt and antifreeze from remaining in the water-cooling tubes or in the water circulation system, causing the laser tubes to work abnormally.