Hazard Tree - No Work Zones

Knowing the exact time a given hazard tree (or compromised section) will fail is extremely difficult, and is, in many cases, an unpredictable task. Given this fact, we need to manage firefighters’ exposure to these hazards by creating a safe work area or No Work Zone (NWZ). The size and extent of the NWZ must be determined by onsite conditions, such as terrain, stand structure, and fire impacts on the tree and adjoining trees.

When an identified hazardous tree or trees cannot be felled, then perform an assessment of which areas have too high a risk, and post a lookout to warn the personnel to stay clear of these areas while working in adjacent areas. If hazard still exists before leaving the area, flag the NWZ so that personnel entering the area will be able to recognize the hazard. Use the following failure zone illustrations as examples to help manage firefighter exposure to these identified hazards. Also, remember to include the possibility of the Domino Effect to surrounding trees.
 

Figure 1 - 1 1/2 X Height of snag	Figure 2 - 1 1/2 X Trunk-to-branch-tip distance	Figure 3 - 1 1/2 X Length of dead top