The EMP Chaff (ElectroMagnetic Pulse Chaff) is a device that combines both electromagnetic pulse technology with chaff functions in one device. It is used to temporarily disrupt anything electrical with an electronic subsystem.
The EMP Chaff appears in Splinter Cell: Blacklist as a ammunition type for the Fourth Echelon Crossbow. Once launched, it will temporarily disable anything electrical nearby - namely, any electrical light system set up within the blast radius. Against bulletproof cameras, this is the best measure, the EMP chaff will make sound while activated, alerting nearby NPCs to your presence. Although this will not work everytime, but EMP Chaff can temporarily disable secruity lasers.
If used during Mark & Execute mode, the EMP Chaff bolt will turn into a non-lethal weapon, however it still has EMP effect that knock out electronics, the sound it makes might alert nearby NPCs.