Revision brings changes to safety standards

The American National Standards Institute standards for safety in arboriculture, or the ANSI Z133 as it is commonly called, have undergone a revision. This process, six and a half years in the making, brings some good changes that affect the production arborist and his daily tasks while climbing, rigging and working from an aerial lift. This article will look briefly at some of the major changes in three categories: overall changes that encompass all phases of production tree work; changes that address the arborist while aloft; and changes pertaining to rigging operations.

Handsaw use is required when rigging and recommended at all other times aloft.
Photos courtesy of Anthony Tresselt.

Overall changes

While many of the changes were in wording and phrasing, they have an impact on how arborists complete their work. Specifically, the Z133 now states that a climbing arborist must always carry two means of being secured and use both whenever it is “determined to be advantageous.” It is important to note that one of the two systems must be a climbing system.

Furthermore, whenever an arborist is working from a stem without a suitable natural branch union the climber must use a tie-in method that prevents the tie-in point (T.I.P) from sliding up or down the stem. This scenario is common in rigging operations, and many suitable, safe, efficient systems exist to meet this requirement.

Finally, in the overall category it is strongly recommended that an arborist aloft always carry a handsaw during work activities.


Lanyards must have a fixed termination or be tied to a rated attachment point on the harness.

Changes pertaining specifically to climbers are basic, but are improvements over the old standard. For instance, positioning lanyards must have a fixed termination on the nonworking end that will not allow that end to pass through the friction management apparatus. This is to prevent the climber from “slipping off” the end of the work positioning lanyard. In the absence of a fixed termination, a climber may also secure the nonworking end to a rated connection point on the climbing harness with an appropriate knot.

If the climbing line is damaged during work, the climber shall secure himself with a lanyard and replace or reposition the rope immediately to remove the damaged section from the climbing system. This requires the climber to inspect his line before descent to ensure there is no damage.

The ground crew is now held responsible for keeping lines free of damage, debris and/or obstruction. They must also notify the climber immediately if any damage has occurred to the climbing line.

Climbers shall inspect rope before descent and secure it if damage is found, and remove or replace the damaged portion of rope from the climbing system.


A few new changes and additions have been included in the protocol for rigging operations. If a rigging point is selected away from the main trunk or parent stem, a secondary means of support should be used. Two examples of this are given: First, a backstay from the rigging point to another section of the tree may be installed; another option is to employ a second rigging line to mitigate and manage forces.

The Z133 now mandates that a drop zone be established before beginning rigging operations. If multiple drop zones are going to be in use, this should be established as well. Furthermore, only necessary crew members should enter the drop zone for assigned tasks and only with the acknowledgment of all crew members involved in the rigging operation. If a crew member has no immediate task, he should be positioned out of harm’s way should a rigging malfunction occur.

All crew members are required to organize and execute work- related tasks so as to not impede or make more hazardous other aspects of the ongoing job. In essence, the standard is addressing job flow, equipment placement and task orders so that all crew members can work safely and efficiently together.

Drop zones shall be established and delineated before work begins.

Climbers are required to design rigging systems that do not contact any of the climber’s life support equipment, nor impede its function, especially when the rigging is in motion or under load. If there is any danger of the trunk splitting above or below the cut when rigging, the climber must take steps to avoid being trapped, pinned or otherwise entangled not only in his climbing system, but also the rigging system should a split occur or the rigging system fail.

Unlike the overall changes, when rigging, workers aloft are required to carry a handsaw while climbing or in an aerial lift. The intent of this is to give the worker the ability to safely make finishing cuts while in awkward positions where chain saw use may be excessively hazardous.


While many of the current revisions may seem obvious or merely a battle of semantics, it is important to keep in mind what the intent of the standard is. No written standard could ever hope to embrace all the possible safe ways to perform tree care operations. Just as it is a truism that arborists never remove the same tree twice, there are as many ways to accomplish our daily tasks in a safe and efficient manner. The sheer variety of trees, tools, equipment, methods, situations and techniques demands that arborists be aware of many hazards on a daily basis. No single one of us can see it all, so it is best to learn from others when we can.

One method of a cinching T.I.P.

Use of a backstay is one method of securing a rigging point on a lateral a distance from the main trunk.

The Z133 gives us a guide or framework within which to place our actions, systems and equipment. By doing that we can judge the effectiveness and level of risk based on incidents that have happened in the past.

In a way, the Z133 is a list of things that can and have gone wrong to others while performing tree work, as well as a list of successful methods. By heeding the “shall” statements and adopting the “should” recommendations when feasible, we can learn how to avoid the pitfalls others have experienced and reap the rewards of good plans executed well by others before us.

How do you get a copy?

Are you a Tree Care Industry Association (TCIA) active member? The TCIA sends each member one copy of Z133 for free as a benefit of membership. The New Z133 may also be ordered from the TCIA by calling 800-733-2622 or going to The Standard may also be ordered through the International Society of Arboriculture (ISA) by calling 800-ISA-TREE. The ISA can offer licensing agreements for organizations that would otherwise need a large number of printed copies.

Tony Tresselt, a writer, ISA certified arborist, TCIA certified tree care safety professional and instructor for North American Training Solutions, works for Arborist Enterprises in Lancaster, Pa.