The principle of operation is based on the circulation of forced hot air at high speed within two concentric chambers. The outdoor area, where hot air circulates at low speed, is called the preheating tunnel since the air in this area is preheated. The interior area, where hot air circulates at high speed, is called the vulcanization tunnel where the profile vulcanization takes place. The air temperature is adjustable up to 400°C. The air speed is also adjustable.