Exhaust fan is almost as important as the laser tube in your machine.
Without proper exhaust the fumes, smoke and smell will stay in the room you have the machine.
Remember to have the fan at the exit of the smoke hose, not close to the machine. This is due to the most fans suck (hah) at creating pressure to push the air out through the hose, if you have it close to the exit the fans only work is to create the negative pressure inside the machine to evacuate the smoke, and you will be off with a smaller fan and less noise.
Parts to buy and where to buy it