High-current arc ignition (HAI)
High-current arc ignition performance is expressed as the number of arc rupture exposures (standardized to the electrode type and shape and electric circuit) that are necessary to ignite a material when they are applied at a standard rate on the surface of the material.
| HAI range | PLC |
| 120 and greater | 0 |
| 60 through 119 | 1 |
| 30 through 59 | 2 |
| 15 through 29 | 3 |
| Less than 15 | 4 |
