Falling Snags

Snags (dead, standing trees without leaves or needles in the crowns) and other hazard trees present a significant hazard to wildland firefighters. Snags typically have much lower fuel moistures than live, green trees; they are subject to rot and they burn more readily. In the process, they often throw firebrands far in advance of the main fire and often burn through more quickly than green trees, falling with little or no warning. Live, green trees that have been weakened by insects, disease, weather, past fires, and age present equal hazard and can fall without warning.

The risk of injuries from hazard trees increases during the night operational period when visibility is greatly reduced.
While the cooler, nighttime period is generally a more effective time to gain control of wildfires, the increased risk from unseen falling snags and weakened live trees may limit the widespread use of crews at night in areas of fire weakened or dead and dying timber.
Environmental conditions that increase risk from hazard trees: Strong winds or erratic winds from storm cells. Night operations. Machine operations. Air operations - cargo drops, water or retardant drops, helicopter take off/landing, low-level flights. Steep slopes. Diseased or bug-killed areas.
Things to consider when assessing the potential dangers of hazard trees: Trees have been burning for an extended period. High-risk tree species (those that are known for rot and shallow root systems) are in the area. Numerous downed trees. Dead or broken tips and limbs overhead. Accumulation of downed limbs. Tree decay, cavities, splits, and cracks. Absence of needles, bark, or limbs. Leaning or hung-up trees. Roots damaged by equipment or erosion.
Mitigation measures to take: Identify and flag all high-risk areas until the hazard has been removed. Keep personnel out of the high-risk areas until the hazard has been removed. Use qualified saw teams and felling bosses. Establish lookouts. Plan a quick and safe escape route. Do not turn your back on a falling tree. Maintain situational awareness.