The number of smoke exhaust pipes is affected by workshop area, number of equipment and machines and ventilation requirements.

1. Workshop area: The larger the workshop area, the more smoke exhaust pipes are needed.

2. Quantity and type of equipment and machines in the workshop: Some machines may produce more waste gas and pollutants, so more smoke exhaust pipes are needed to treat waste gas.

3. Ventilation requirements: According to national and regional building codes and standards, the ventilation design of the workshop should meet certain codes and standards. This will also affect the number of smoke exhaust pipes required.