The “Punch” is the extra amount of water that can be placed and held on the flaming fire perimeter and adjacent fuels. It can absorb and overcome levels of heat attack that water and foam cannot. This is especially critical within the first ten minutes after a direct attack drop. With most fires being fought in the direct attack mode, Firewall II offers increased certainty of knockdown from single applications and the ability to directly take on greater fire intensities that is not possible with water or foam.
In the following example, Firewall II, even at a low mix ratio of 0.5%, maintains fuels above the moisture of extinction level for at least ten minutes, while water and foam evaporate almost immediately, leaving little product available for heat absorption.
Always more effective then plain water
- Has fewer drift and evaporation losses when dropped from aircraft, resulting in more product on target
- Clings to vegetation better than other products
- Holds more water on fuels for a longer period of time
- Less absorption into soil and ground litter means more water available for heat absorption
Determining the most effective mix ratio
- USFS has approved Firewall II at mix ratios 0.25% – 3.0%
- Effective mix ratio is a balance between three properties; adhesion, cohesion and viscosity – a blend of art and science
- Desired effect in fuel types
- Thicker: lasts longer
- Thinner: better uniform coverage
- The most effective balance between adhesion, cohesion and viscosity can be found by varying mix ratios to provide the greatest retention of suppressant in the wildland fuel canopy while still allowing penetration through the canopy to treat the ground litter.
- Firing from wet line
- Control fire behavior (intenisity) at burnout/backfire operations
- Keep fire out of canopy
- Containmmnet of spots
- Defensive wet line quickly and extended easely.
- Line building support
- Hot spots and flarups