Snags (dead, standing trees without leaves or needles in the crowns) and green hazard
trees present a significant threat to wildland firefighter safety. Snags typically have much
lower fuel moistures than live, green trees; and they burn more readily. In the process, they
often throw off embers creating spot fires in advance of the main fire. Snags may burn
through more quickly than green trees and can fall without warning. Live, green trees
weakened by insects, disease, weather, fire, and age presents another hazard and they can
also fall without notice.
Night Operations: The risk of serious injuries from hazard trees may increase during the night operational period
when visibility is reduced. While work in cooler, nighttime environments can help control efforts, it also presents an increased risk from unseen falling snags and weakened live trees. Night operations should be
restricted in areas of high risk rated dead and dying trees.
Environmental conditions that increase risk from hazard trees: Strong or gusty winds from
storm cells. Air operations - water or retardant drops, rotor wash from helicopters. Steep
slopes with rolling material. Erosion and undercut root systems. Diseased or bug-killed areas
(Mountain Pine Beetle).
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) in the area. Numerous downed trees/material. Broken tops and dead
limbs overhead. Accumulation of downed limbs, tree decay, cavities, splits, cracks, lack of
needles, bark, limbs or other indicators of overhead hazards. Roots damaged by equipment,
fire or erosion create hazards.
Mitigation measures to take: Identify and establish No-Work-Zones (NWZ) in all high-risk
areas until the hazard has been mitigated. Instruct firefighters of established NWZ in briefings.
Identify with flagging/signs, and show area on maps. Establish lookouts to protect NWZs.
Assign only qualified sawyers and Falling Bosses. Order additional professional fallers in
advance. Use heavy equipment, and blasters when appropriate. Plan a quick and safe
escape routes. Do not turn your back on a falling tree or known hazard. Use lookouts to
maintain secure felling areas. Maintain situational awareness.
6 Minutes Home
References: Hazard Tree Safety Web Page
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