 In a flanking fire, personnel set lines of fire directly into the wind. The intensity of flanking fires is moderate with less intensity than heading fires but more intensity than backing fires. The intensity can be manipulated by adjusting space between the lines. Lines closer together will be less intense while lines farther apart will be more intense. Just as with strip head fires, the intensity will increase when the two lines converge. Flanking fires require more personnel because all workers must carry the drip torch at the same time and walk the same speed. Flanking fires are used when winds are steady. Swirling winds can quickly turn a flanking fire into a strip head fire.