High voltage arc tracking rate (HVTR)
High voltage arc tracking rate is denoted as the rate, in millimeters per minute, that a tracking path can be produced on the surface of the material under standardized test conditions. A note is made if ignition on the material takes place. The results of testing the nominal 3 millimeter thickness are considered representative of the material's performance in any thickness.
| HVTR range | PLC |
| 0 through 10 | 0 |
| 10.1 through 25.4 | 1 |
| 25.5 through 80 | 2 |
| 80.1 through 150 | 3 |
| Greater than 150 | 4 |
