When Using Nebulizers, Where Should You Place Them to Minimize

When using nebulizers, where should you place them to minimize risk of contamination?

A) in the inspiratory limb only, at a high point in the circuit
B) in both the expiratory and inspiratory limbs, at high points in the circuit
C) in the expiratory limb only, at a low point in the circuit
D) in both the expiratory and inspiratory limbs, at low points in the circuit