Good Mr. Josue, TELGOPOR is an excellent thermal and acoustic insulator, it does not present fire risks Remember that to make an air duct, you must take into account certain rules of movement and displacement of air so that the air flow reaches the room with some force. When putting the duct in the room that is going to be cooled, you must also put a return so that the air circulates inside the room, that is to say that between cold air and the acond air it returns to cool it again and thus keep that cycle you put a rack at the door of the room to do that cycle. You have to get a glue compatible with Telgopor to be able to join the parts of the pipe that you are going to manufacture. Friend in the Network you can get enough information about the Pro and the Cons of the use of Telgopor in the Home. Here in my country is widely used polyurethane or P3 sheets for the manufacture of ducts. Telgopor is Expanded Polystyrene and P3 is Expanded Polyurethane. They are quite similar, but the P3 Expanded Polyurethane is better insulating and is more dense and less fragile. you should look online for this Polyurethane vs Polystyrene there you will have information.