These Edwards nXDS replacement exhaust silencer element spares are used to reduce the operating noise of the scroll pump. They are effective at dampening the roughing sound that is heard when the pump starts to evacuate the chamber, they act as a vacuum pump muffler. These Edwards nXDS exhaust silencers are designed to vent into the room and should only be used on nXDSi series pumps that are evacuating air from a clean vacuum chamber. They should not be used with chemical series nXDS-ic pumps that are used on chemical applications. These Edwards nXDS replacement exhaust silencer elements should be replaced every year during preventive maintenance (PM) as they capture the pump's exhausted tip-seal dust and will eventually become clogged.