The purpose of setting two ventilation holes on the tea roaster is to realize good ventilation and air exchange, so as to ensure that the temperature and humidity of the roasting process are controlled within the appropriate range. The following are the recommendations for the two ventilation holes:

1. Upper Ventilation Hole: There is an upper ventilation hole on the top of the roaster, which is usually in the shape of a circle or a long strip. The purpose of this vent is to exhaust the smoke and heat generated during the roasting process and prevent the temperature in the roasting room from getting too high.

2. Bottom vent: set up a bottom vent at the bottom of the tea roasting and flavoring machine, usually in the form of a long strip or mesh. The function of this vent is to introduce fresh air, help regulate the air flow and humidity in the room, and maintain air quality and humidity control during the roasting process.

It is important to note that the size and location of the air vent should be adjusted according to the specific design of the roaster and the roasting requirements of the tea. More specific air vent settings can be made by consulting a professional roasting equipment manufacturer or according to the tea roaster's manual.

In short, through the reasonable setting of the upper and bottom air vent, you can effectively realize the ventilation and air exchange in the tea roasting and flavoring machine, and improve the quality of tea roasting.