1. During the use of the jar, the use of the jar should be checked at any time every day. On the premise that there is liquid nitrogen in the jar, if there is water droplets or frost on the lid and upper part of the jar, it indicates that there is a problem with the quality of the jar. stop using it immediately;

2. When there is no water droplets or frost on the bottle cap and upper part of the jar, touch the outer shell with your hand and feel that the upper part is cold and the lower part is hot, indicating that there are some problems with the quality of the jar, that is, the daily increase and loss of liquid nitrogen is relatively large, so you should pay attention to it. To prevent the stored material from being damaged after the liquid nitrogen is consumed, it is best to stop using it when necessary; if the upper and lower temperatures are the same, it means that the quality of the jar is no problem.

3. After opening the cork, the mist in the bottle mouth does not overflow, but sinks, indicating that the jar is good.

4. Use your ear to listen to the sound of bubbles in the jar from the mouth of the bottle. If it is frequent, there is a problem with the quality of the jar, otherwise there is no problem.