Tree Climbing and Rigging Safety

Tree climbers do not work the way roofers or ironworkers do. Their anchor is a living thing that may have hidden decay. They move constantly. They cut with a saw while hanging from a rope and lower wood heavy enough to pull a tree apart. That is why tree work has its own safety standard, ANSI Z133. Construction fall protection rules do not fit it. Reading this will not make you a climber. You need supervised, hands-on training before you leave the ground, and you need to prove your skills to a qualified trainer. Use this to learn the rules and the reasons for them.

What You Will Be Able to Do

• Explain which rules apply to tree work
• Run a job briefing and inspect a tree before climbing
• Name the parts of a climbing system and inspect them
• Explain the rules for using a saw aloft
• Set up a drop zone and communicate with your crew
• Describe how rigging loads act on a tree
• Respond to electrical contact and a climber in trouble

The Rules That Apply

ANSI Z133 is the US safety standard for arboricultural operations. The current edition, Z133-2026, was published in May 2026 and replaces the 2017 edition. It replaces the old electrical categories with four qualification levels and adds radiofrequency awareness training. ISA offers the digital edition free for individual use, so read it and make sure your company's procedures match.

OSHA has no standard written just for tree care. It can still cite employers under other rules, including its general duty to keep a workplace safe. Its electric power rule covers line-clearance tree trimming. Inspectors often look to Z133 as the accepted practice. Some states have their own tree work rules, and these can be stricter.

Job Briefing

Hold a job briefing before work starts, and repeat it if conditions change. Everyone should know:

• What is being done, and in what order
• Who does what, and who is in charge
• Where the hazards are: power lines, traffic, buildings, and bad wood
• Where the drop zones are
• What gear is needed
• How you will talk to each other
• What the emergency plan is, including the site address and who can do a rescue

Inspecting the Tree

Check every tree before you climb, and keep looking as you go up.

1. From a distance: Walk around it. Look at the lean, dead tops, and hangers, which are broken limbs lodged in the crown.
2. At the base: Look for root plate lift, fungus, cracks, and cavities. Sound the trunk with a mallet to find hollow spots.
3. In the crown: Check the tie-in point and any limbs you will rely on.
4. Around it: Look for wires, buildings, traffic, and insect nests.
5. Species and season: Some wood is brittle, and dead trees can fail with little warning.

If the tree is not safe to climb, use a lift or a crane, or call in someone with more experience. You always have the right to say no.

Climbing Systems

A climbing system holds you and lets you move.

Use only gear rated for climbing and tree work. Follow the maker's rules for use and retirement. Retire anything you are unsure about, and do not mix parts that are not meant to work together. Keep a log if your company requires it. Keep climbing gear away from chemicals, saw fuel, and direct contact with a running saw.

Tie-In Point

Your tie-in point is what you are hanging from. Choose a live, sound limb or stem that can take your weight plus the shock of a fall. Test it before you commit. Do not trust dead limbs. Set it high enough to keep you working above your tie-in as little as possible.

Staying Tied In

Stay tied in from the moment you leave the ground until you are back on it. That includes moving around the crown. When you move to a new tie-in point, attach the second line before you detach the first. This is the same rule that keeps people safe in any rope work.

Spikes, also called gaffs or climbers, are for removals. Using them on a tree you plan to keep leaves wounds up the trunk.

Saws Aloft

A saw near your climbing line is one of the most serious risks in tree work.

• Be secured twice. Tie in with a climbing line and a second attachment such as a lanyard before you cut. Some state rules spell this out, and they do not count both ends of one lanyard as two.
• Start it safely. Start the saw on the ground and send it up, or start it aloft only from a secure, balanced position with the chain brake on. Never drop-start it.
• Keep the brake on when you move. When you are not cutting, set the brake or shut off the saw.
• Handle it correctly. Use both hands with a top-handle saw. Top-handle saws are for trained climbers, and only for use aloft.
• Support the weight. Hang heavier saws from a separate line, not from your saddle.
• Watch your lines. Know where every rope is before each cut. Keep your lanyard and climbing line out of the cut.

Drop Zones

A drop zone is the area where falling wood or tools can land. Mark it with cones, signs, or barriers. Nobody enters it until the climber confirms that it is safe.

Use a set command and response every time. For example:

1. Before each cut, the climber calls: "Stand clear."
2. The ground worker checks the zone and answers: "All clear."
3. Only then does the climber cut.

It works the same way in reverse. A ground worker who needs to enter the zone calls up first and waits for the climber to stop and answer. Silence never means yes. If noise makes that hard, use radios or hand signals that everyone has agreed on.

Rigging

Rigging lowers a piece on a rope when it cannot simply drop. It looks simple, but the forces are large.

• Load: Green wood is heavy. A 6-inch limb that is 10 feet long can weigh 150 to 200 pounds, and species and moisture change that.
• Shock: A falling piece caught by a rope pulls far harder than its weight. The longer it falls before catching, the larger the force.
• Pulley effect: The rigging point can carry about double the load, because the rope pulls on both sides.
• The tree: Forces can break a limb or even a trunk. A weak or decayed tree must not be rigged from. A tree can also snap at the base.

Good practices:

• Use a separate rigging line, never your climbing line.
• Choose a rigging point above the piece, on sound wood, and not one that you hang from.
• Use blocks, pulleys, and slings rated for the load, and inspect them.
• Cut smaller pieces if you are not sure.
• Control the line with a friction device at the base of the tree, operated by someone trained to use it.
• Keep people out from under the load and out of the bight of the rope, which is any loop or bend that could snap tight.
• Talk through every cut before you make it.

Overloaded rigging is a common cause of serious accidents. Advanced rigging and crane work are specialties that need extra training.

Aerial Lifts

A bucket truck gives you a work platform, not a free pass.

• Only trained, authorized people run a lift.
• Set up on firm, level ground with outriggers and chocks.
• Wear a harness and lanyard attached to the point set by the maker.
• Do not tie off to the tree.
• Stay within the rated load, counting yourself, tools, and wood.
• Set up traffic controls.

Insulated booms do not make you safe around power lines. Dirt, wet ropes, and metal tools can carry current.

Electrical Hazards

Most electrical injuries in tree care come from contact through a tree, a tool, or a rope. Treat every wire as energized until a qualified person says otherwise.

Z133-2026 sorts workers into four electrical levels:

If you are unqualified, you, your tools, and the branches you cut must stay at least 10 feet from conductors up to 50,000 volts, and farther for higher voltages. If a tree is within reach of a line, stop and call for a qualified crew. Only trained line-clearance arborists do that work.

If a person is in contact with a line or a tree that is touching one, do not touch them. Call 911 and the utility, and keep everyone back. Wet ground may carry current. Only a trained person who knows the line is de-energized should go near them.

Emergencies

Crews must be able to rescue a climber. Do not wait until an accident to find out who can do it. Plan who climbs, what gear stays ready, and how you will lower someone. Practice on a schedule, because climbers hanging in a saddle can get worse quickly.

1. Stop work and shut down saws.
2. Call 911 and give the site address.
3. Check for hazards. Do not become a second victim. Check for electricity first.
4. Make contact with the climber.
5. A trained rescuer climbs or uses a lift, and lowers the climber.
6. Give first aid. Press hard on any bleeding.

Everyone on the crew should know first aid and CPR. Keep a kit on the truck that can handle heavy bleeding. Report near misses, too. They are free lessons.

Common Mistakes

Check Your Understanding

1. A roofer says you should tie off the way they do. Why do tree workers follow different rules?

Their anchors and movement are different. Trees are living anchors, climbers move constantly, and cutting creates other hazards. ANSI Z133 covers those.

2. You are ready to make a cut, and you have only your climbing line attached. What do you do?

Attach a second line, such as a lanyard, before you cut. That way, a cut line does not mean a fall.

3. A ground worker walks under you while you are cutting. What should happen?

Stop cutting. Nobody enters the drop zone until the climber confirms, and nobody cuts until everyone is clear.

4. A limb will fall 4 feet before the rope catches it. What does that do to the force on the rigging point?

It multiplies the force, since a falling piece pulls much harder than its weight. Cut a smaller piece or reduce the fall.

Key Takeaways

• Tree work follows ANSI Z133, and the 2026 edition is now current.
• Do a job briefing and inspect the tree before you climb.
• Stay tied in the whole time, and be secured twice when using a saw.
• Use a command and response for every drop zone.
• Rigging forces are far larger than the weight of the wood.
• Unqualified workers stay at least 10 feet from conductors.
• Practice aerial rescue before you need it.