When the purity of carbon dioxide gas is not enough, some spatter particles will accumulate on the contact tip and the shroud for a long time. If the cleaning is not timely, it will hinder the normal ejection of gas and damage the normal protection of the airflow cover, plus an artificially elongated arc. As a result, the protection air flow drifts and diverges, allowing outside air to enter the arc zone. The opportunity to create other stomata is also greater. Such as: nitrogen hole, hydrogen hole.