| Empirical Relationship | Fuel type | lf (m) | Range in IB (kW∙m−1) |
| Burrows | Eucalypt forest |
| 37 - 4368 |
| Butler et al. | Jack pine forest |
| - |
| Byram | Pine litter |
| 56 - 2232 |
| Catchpole et al. | Shrublands |
| 100 - 77,000 |
| Clark | Grassland |
| 65 - 12,602 |
| Fernandes et al. | Maritime pine forest |
| 30 - 3527 |
| Fernandes et al. | Shrublands |
| 12 - 7605 |
| Nelson | Southern USA fuel |
| 5 - 3320 |
| Nelson and Adkins | Litter and shrubs |
| 98 - 2755 |
| Van Wilgen | Fynbosshrublands |
| 194 - 5993 |
| Vega et al. | Shrublands |
| 294 - 6905 |