The Comparative Tracking Index or CTI is used to measure the electrical breakdown (tracking) properties of an insulating material. To measure the tracking, 50 drops of 0.1% ammonium chloride solution are droped on the material, and the voltage measured for a 3mm thickness is considered representative of the material performance. The term electrical breakdown has several similar but distinctly different meanings. ... This article or section is in need of attention from an expert on the subject. ... Ammonium chloride or Sal Ammoniac (chemically ammonium chloride (NH4Cl); also nushadir salt, zalmiak, sal armagnac, sal armoniac, salmiakki, salmiak and salt armoniack) is, in its pure form, a clear white water-soluble crystalline salt with a biting taste. ...

Tracking is an electrical breakdown on the surface of an insulating material. A large voltage difference gradually creates a conductive leakage path across the surface of the material by forming a carbonized track.

Performance Level Categories (PLC) were introduced to avoid excessive implied precision and bias.