ANSI Z133-2026: the four electrical levels and the tables they read
Updated: Sep 21
ANSI Z133-2026 took effect May 27, 2026 and sorts everyone working near a conductor into four Electrical Levels: unqualified, qualified to 750 volts, qualified to 35 kV, and line clearance qualified for all voltages. Each level reads its own approach distance table, and above a level's voltage ceiling that table prints the unqualified distance.
A 12 kV feeder runs across the back of a property. Four people are working under it on the same morning:
a groundman feeding a chipper
a residential arborist hired by the homeowner
a second residential arborist whose employer trained and tested them for primary voltage work
a utility line clearance trimmer on a separate circuit patrol
Under ANSI Z133-2026 those four people owe four different distances to the same conductor: 10 feet, 10 feet, 2 feet 10 inches, and 2 feet 3 inches. None of them is reading the same table. Until May 27, 2026 there were three tables in that section and three categories of person, not four.
That is the change worth knowing about. The 2026 edition of Z133 replaced a two-way split that had stood for decades with a four-level ladder, gave each level its own minimum approach distance table, and moved most of the section numbers that training decks, job briefings and enforcement memos still cite. Everything below is what the current edition says, where it differs from what your 2017 copy says, and where it is not the rule that binds you at all.
What the standard is and what it is not
Z133 is an American National Standard developed under the Accredited Standards Committee Z133, whose secretariat has been held by the International Society of Arboriculture since November 1969. The committee was organized on April 4, 1968 after Ethel M.
Hugg of Johnstown, New York wrote to federal and state authorities following her son's death while pruning trees. The first standard was adopted by the committee on July 14, 1971 and approved as an American National Standard on December 20, 1972. It has been revised in 1978, 1982, 1987, 1994, 2000, 2006, 2012, 2017, and now 2026.
It is not a regulation. Section 1.2 says so plainly: the standard "is intended as a guide to federal, state, and local authorities in drafting their regulations and may be adopted in whole or in part." Nobody is cited for violating Z133.
People are cited for violating a regulation that borrowed from Z133, for breaching a contract that named Z133, or under the General Duty Clause in a proceeding where Z133 is the evidence that the hazard was recognized. Those three routes are covered further down, because the distinction matters more in a deposition than it does on a tailboard.
Two conventions govern how you read it. The standard defines shall as "a mandatory requirement" and should as "an advisory recommendation." Both words appear in the same subsection constantly, and the difference is the whole content of a compliance argument. Section 4.1.6, for instance, says climbing arborists should ascend and descend on the side of the tree away from energized lines. Section 4.1.8 says the arborist's body, tools, and conductive gear shall maintain the minimum approach distance. One of those is a preference and one is the line.
The second convention is easier to miss. The Foreword states: "There are ten annexes in this standard. All ten are informative and are not considered part of this standard." That includes Annex A, the glossary that defines every boldface term, Annex B, the training outline that many programs treat as a curriculum requirement, and Annex H, the electrical hazard abatement guidance. Useful, referenced throughout, and not requirements. A specification that says "trained per Z133 Annex B" is requiring conformance with something the standard itself declines to require.
ISA distributes the 2026 edition as a free PDF for individual use, in English and Spanish, and sells print copies at $29.95, or $24.95 for members. There is no longer a cost argument for a crew not having it.
The 2026 edition, and the section numbers it moved
Electrical hazards were Section 4 in the 2017 edition and are Section 4 in the 2026 edition. Almost nothing else about that section survived intact.
In 2017 the section had three parts:
Section | Title | Cross-referenced to |
4.1 | General | |
4.2 | Working in Proximity to Electrical Hazards, Incidental Line Clearance | 29 CFR 1910 Subpart S |
4.3 | Working in Proximity to Electrical Hazards, Utility Line Clearance | 29 CFR 1910.269 |
Two categories of person, two tables, one distinction: are you working for the utility or not.
In 2026 there are five parts. 4.1 General, then 4.2 through 4.5, one per Electrical Level. The 2017 incidental category split in two. The 2017 utility category kept its distances and changed everything else about how it is cited: its name, its subsection number, and its table number, which went from Table 3 to Table 4.
Other renumbering matters for anyone maintaining a spec. Vehicle operations is Section 5 in both editions, but cranes moved from 5.7 to 5.6.6, which is why a specification citing Z133 section 5.7.11 for crane hoisting now points at nothing. Climbing is Section 8 in both, but the anchor point requirement moved from 8.1.11 to 8.2.11. If your contract, your training deck or your job hazard analysis cites Z133 by section number, every one of those citations needs to be checked against the current edition rather than assumed forward.
The title changed too: the standard was Safety Requirements for Arboricultural Operations and is now Safety and Health Requirements for Arboricultural Operations. The designation changed too. The 2006 edition was ANSI Z133.1-2006 and the 2012 edition was ANSI Z133-2012, which is why older citations carry an extra digit that no current edition uses.
Four electrical levels and the word that sorts them
The four levels, as Section 4 names them:
Electrical Level 1 Arborist, Unqualified for Any Voltages (4.2). Someone who has had electrical hazard awareness training but no related on-the-job experience and no demonstrated competency near any voltage. Section 4.2.2 is blunt: "They shall not perform work where electrical hazards exist." Section 4.2.5 adds that there shall be no direct or indirect contact with supply lines, communication lines, or equipment, "regardless of whether they are energized or deenergized and grounded." A Level 1 reads Table 1 and stays outside it.
Electrical Level 2 Arborist, Qualified for Voltages of 750 V or Less (4.3). The subsection carries a note: "Formerly: Incidental Line Clearance." Trained, experienced, familiar with the equipment, and demonstrably competent near secondary voltage. Reads Table 2.
Electrical Level 3 Arborist, Qualified for Voltages Up to 35 kV (4.4). Same note, "Formerly: Incidental Line Clearance." Same structure of training and demonstrated competency, extended to primary distribution voltage. Reads Table 3.
Electrical Level 4 Arborist, Line Clearance, Qualified for All Voltages (4.5). Annex A states the equivalence directly: "Equivalent to OSHA's 'line-clearance tree trimmer' in 1910.269(r)." Reads Table 4.
Level 4 also carries a staffing rule the other three do not. Section 4.5.15 requires a second Level 4 Arborist or trainee, trained at minimum in emergency procedures, to be "within unassisted voice communication," and recommends visual contact. Both apply whenever the arborist aloft must approach closer than 10 feet to any energized line above 750 volts, whenever vegetation that cannot first be cut with an insulating pole tool is being removed, or whenever roping is required.
The trigger is the 10 foot mark, not Table 4's much shorter distance, so on a 12 kV feeder the second person is required from 10 feet inward even though the climber may lawfully work to 2 feet 3 inches. Outside line clearance, section 3.4.7 sets a lower bar: a second arborist, trainee or worker trained in emergency procedures within visual or voice communication for any work above 12 feet. What that second person has to be ready to do is its own subject.
The word that sorts Level 2 and Level 3 from Level 4 is not skill and it is not voltage. It is purpose. Section 4.5.2 defines the Level 4 Arborist as one who works "for the purpose of clearing space around the electric supply lines and equipment on behalf of the utility or organization that controls or operates the lines or equipment."
The Level 2 and Level 3 definitions are the same sentence with that clause negated: an arborist near an electrical hazard "who is not working for the purpose of clearing space around the electric supply lines on behalf of the utility."
A tree crew and a line clearance crew can do identical work on the same afternoon at the same voltage, and which table they read is decided by who hired them and why. That gate is the same one the federal standard draws, and it is the one people get wrong most often.
The federal cross-references follow the same split. Sections 4.3.3 and 4.4.3 require the employer to verify Level 2 and Level 3 competency "consistent with OSHA 29 CFR 1910, Subpart S." Section 4.5.3 requires Level 4 competency to be verified "consistent with OSHA 29 CFR 1910.269(a)(2) training requirements." Z133 is not inventing a parallel qualification scheme. It is putting its own names on the tiers the federal standard already has.
Section 4.1 binds all four levels
Before any of the four subsections applies, section 4.1 applies, and section 4.1.1 pulls all of Section 3, General Safety Requirements, in with it. Six items in 4.1 decide more field arguments than the tables do.
What the training has to cover. Section 4.1.2 lists six things electrical hazard training "shall include, but is not limited to." The first is the approach distance for the maximum voltage in the area "as well as the skills and techniques necessary to maintain that distance." That is the difference between a worker who can recite 10 feet and one who can hold it while lowering a limb. The rest are recognition items:
Supply lines are energized under normal conditions.
In storms or abnormal system configurations, all wires and cables, communication lines included, may carry deadly voltages.
The human body is conductive.
Vegetation is conductive.
Step potential and touch potential are forms of indirect contact.
An electrical training record that does not touch those six is short of the standard on its face.
Who calls the hazard. Section 4.1.3 requires a qualified arborist to inspect the worksite for electrical hazards before work, and to "consult with the electrical system owner/operator if uncertain about the presence or nature of an electrical hazard." Uncertainty is not a reason to proceed carefully. It is a reason to make the call.
What has to hold the distance. Section 4.1.8 puts the arborist's body, tools, equipment and "conductive gear (including, but not limited to, climbing lines, rigging lines, throwlines)" inside the minimum approach distance requirement. A throwline crossing a primary is a violation of the same sentence that governs a hand.
What the distance does not care about. Section 4.1.16 keeps the distance in force "when working in proximity to energized electric supply lines with insulated covers, blankets, hoses, sleeves, or any other covering or coating." On a California circuit rebuilt with covered conductor, the covering buys the crew nothing under Z133.
Sections 4.1.14 and 4.1.15 remove two more comfort blankets: rubber gloves, with or without leather protectors, and dielectric or electrical-resistant footwear "shall not be considered as providing any measure of safety from electrical hazards." Section 4.1.17 requires pole tools used in proximity to energized lines to be built of fiberglass reinforced plastic or wood.
When to stop for weather. Section 4.1.13 prohibits work in proximity to energized lines "during adverse weather conditions, such as thunderstorms, high winds, snowstorms, or ice storms." The note under it puts numbers on high wind: winds over 40 mph, or over 30 mph where material handling is involved, meet the criterion unless the employer takes precautions against the wind's effects. Those figures sit in a note, which is informative, so the requirement is the judgment and the numbers are the guidance.
When the truck gets too close. Section 4.1.11 is the one people have not usually heard. If the distance between the aerial device and a supply line closes inside the required approach distance, the worker aloft shall warn the equipment operator and the ground crew. The warning shall also "direct them to keep clear of the vehicle and attached equipment (e.g., chipper) until MAD is visually established and communicated." Step and touch potential means the hazard reaches the chipper at the tailgate, not just the boom.
Each qualified level then adds its own stop-work rule. Sections 4.3.13, 4.4.13 and 4.5.18 all say that when the approach distance cannot be maintained, work stops and the supervisor develops an abatement plan with the system owner/operator's designated supervisor. Section 4.1.4 says the same for storm and emergency work. What that plan has to contain is set out in Annex H, which is informative.
The four tables, and one 12 kV span read four ways
Table 1, Electrical Level 1. Applies to everyone unqualified for any voltage.
Nominal voltage, phase to phase (kV) | MAD (ft in) | Meters |
50.0 and less | 10-00 | 3.05 |
50.1 to 72.5 | 11-00 | 3.35 |
72.6 to 121.0 | 12-08 | 3.86 |
121.1 to 145.0 | 13-04 | 4.06 |
145.1 to 169.0 | 14-00 | 4.27 |
169.1 to 242.0 | 16-08 | 5.08 |
242.1 to 362.0 | 20-08 | 6.30 |
362.1 to 550.0 | 26-08 | 8.13 |
550.1 to 800.0 | 35-00 | 10.67 |
Table 2, Electrical Level 2. Adds two rows below 750 volts and is otherwise Table 1.
Nominal voltage, phase to phase (kV) | MAD (ft in) | Meters |
0.300 and less | Avoid contact | Avoid contact |
0.301 to 0.750 | 1-06 | 0.46 |
0.751 to 50.0 | 10-00 | 3.05 |
50.1 and above | as Table 1 | as Table 1 |
Table 3, Electrical Level 3. Adds three primary distribution rows and is otherwise Table 1.
Nominal voltage, phase to phase (kV) | MAD (ft in) | Meters |
0.300 and less | Avoid contact | Avoid contact |
0.301 to 0.750 | 1-06 | 0.46 |
0.751 to 5.0 | 2-09 | 0.84 |
5.1 to 15.0 | 2-10 | 0.86 |
15.1 to 35.0 | 3-04 | 1.02 |
35.1 to 50.0 | 10-00 | 3.05 |
50.1 and above | as Table 1 | as Table 1 |
Table 4, Electrical Level 4. The line clearance table, printed in the standard with three altitude columns. The sea level to 5,000 foot column:
Nominal voltage, phase to phase (kV) | MAD to 5,000 ft (ft in) | Meters |
0.300 and less | Avoid contact | Avoid contact |
0.301 to 0.750 | 1-02 | 0.36 |
0.751 to 5.0 | 2-03 | 0.69 |
5.1 to 15.0 | 2-03 | 0.69 |
15.1 to 36.0 | 2-08 | 0.81 |
36.1 to 46.0 | 2-11 | 0.89 |
46.1 to 72.5 | 3-06 | 1.07 |
72.6 to 121.0 | 3-11 | 1.20 |
121.1 to 145.0 | 4-06 | 1.37 |
145.1 to 169.0 | 5-01 | 1.55 |
169.1 to 242.0 | 7-00 | 2.13 |
242.1 to 362.0 | 11-09 | 3.58 |
362.1 to 420.0 | 14-08 | 4.47 |
420.1 to 550.0 | 17-06 | 5.33 |
550.1 to 800.0 | 23-09 | 7.24 |
Two more columns run alongside that one in the standard, for 5,000 to 10,000 feet and 10,000 to 14,000 feet. Anyone working above 5,000 feet needs the printed table rather than this column, and needs to know that the federal altitude arithmetic does not produce a single answer above that elevation.
Back to the 12 kV feeder. Level 1 reads Table 1 and owes 10 feet. Level 2 reads Table 2 and also owes 10 feet, because 12 kV sits in the 0.751 to 50.0 row. Level 3 reads Table 3 and owes 2 feet 10 inches. Level 4 reads Table 4 and owes 2 feet 3 inches at sea level. The spread between the outermost and innermost person under that span is 7 feet 9 inches, and every foot of it is a qualification question rather than an engineering one.
Above your level's ceiling, the table prints the unqualified number
This is the single mechanic to carry off the page. Each table gives real working room only up to its level's voltage ceiling. Above that ceiling, the same table prints the Level 1 distance.
Table 2 gives a Level 2 Arborist 1 foot 6 inches at 480 volts and 10 feet at 12 kV. Table 3 gives a Level 3 Arborist 2 feet 10 inches at 12 kV and 10 feet at 46 kV. The Annex A definitions say the same thing in words. A Level 2 Arborist "must not bring their body or any conductive material closer than 10 ft (3.05 m) to primary electric supply lines exceeding 750 V." A Level 3 Arborist must not do so on lines exceeding 35 kV.
The practical consequence is that qualification is per voltage, not per person. A Level 3 Arborist is not a person who may work close to conductors. A Level 3 Arborist is a person who may work close to conductors up to 35 kV, and who on the 69 kV subtransmission line two spans over stands exactly where the unqualified groundman stands. On a joint corridor with distribution underbuilt beneath subtransmission, that is two different numbers on the same pole for the same climber on the same job.
What the 2026 edition cost a 69 kV span
The 2017 edition did not work that way, and this is the change most likely to catch a residential or municipal operation that never touched utility work.
Z133-2017 Table 2, headed "Approach distances for incidental line clearance," ran the full voltage range. It gave a qualified incidental line clearance arborist 3 feet 8 inches at 36.1 to 46.0 kV and 4 feet 4 inches at 46.1 to 72.5 kV. A non-utility arborist trained under that edition could work within 4 feet 4 inches of a 69 kV conductor.
Z133-2026 caps Level 3 at 35 kV. Table 3 prints 10 feet at 35.1 to 50.0 kV and, in the rows it shares with Table 1, 11 feet at 50.1 to 72.5 kV. The same arborist, the same 69 kV conductor, the same tree: 4 feet 4 inches until May 26, 2026, and 11 feet from May 27.
That is 6 feet 8 inches of working room removed in a single edition, and no amount of additional training restores it, because there is no level between 35 kV and line clearance. Above 35 kV, non-utility work near the conductor is not a qualification problem any more. It is a stop-work-and-call-the-utility problem.
Table 4 did not move and neither did its source
The line clearance numbers are the one part of Section 4 that carried forward unchanged. Table 4 of the 2026 edition reproduces Table 3 of the 2017 edition foot for foot and inch for inch, across all three altitude columns and all fourteen voltage bands.
The two edits are cosmetic. The 2017 first row read 0.050 to 0.300 kV and the 2026 first row reads 0.300 kV and less, which closes a gap below 50 volts rather than changing any distance, and the metric column was rounded from three decimal places to two.
The reason it did not move is printed under the table: "From 29 CFR 1910.269, Tables R-6 and R-7, altitude corrected (R-5) for 1,500 m, 3,000 m, and 4,200 m." Z133 is not setting a line clearance approach distance. It is reprinting the federal one. A Level 4 Arborist who complies with Table 4 at sea level is complying with 1910.269, and an employer who computes its own distances under the federal rule is not obliged to produce Table 4's figures, only distances at least as protective.
That footnote also inherits a live question. The table numbers it cites are the ones 1910.269 used before the 2014 final rule, and which table number carries the approach distances today is genuinely contested in OSHA's own material. Z133's numbers are right. Its pointer is aging.
Where Z133 Table 1 and Cal/OSHA Table 1 disagree
In California the enforceable approach distance for anyone who is not a qualified line clearance tree trimmer or trainee is Table 1 of Title 8 section 2950, not Z133 Table 1. The two tables have the same purpose, similar bands, and different numbers.
Voltage | 8 CCR 2950 Table 1 | Z133-2026 Table 1 |
69 kV | 10-09 | 11-00 |
115 kV | 12-04 | 12-08 |
138 kV | 13-02 | 13-04 |
161 kV | 14-00 | 14-00 |
230 kV | 16-05 | 16-08 |
345 kV | 20-05 | 20-08 |
500 kV | 26-08 | 26-08 |
800 kV | 35-00 | 35-00 |
Z133 is equal or further out in every band. On a 115 kV line the gap is 4 inches. Below 50 kV, where most distribution clearing happens, both say 10 feet and there is nothing to reconcile.
There is one place Z133 is better to read from. California's table skips six windows of voltage, printing nothing at all for a circuit that lands in one of them. Z133-2026 closed every one of those windows: its bands run continuously from 50.1 kV to 800 kV. A circuit that lands in one of California's gaps has an answer under section 2951(a), but Z133's continuous bands give the same answer without an argument. Take the larger of the two figures and the question does not arise.
In California the low voltage line is 600 volts
Z133 draws its Level 2 ceiling at 750 volts. California does not. Exception No. 1 to section 2950 permits a qualified tree worker to trim within 10 feet, but no closer than 1 foot, of "energized low voltage (600 volts or less) power lines and conductors." A 480 volt service drop is low voltage in both systems. A 690 volt circuit is low voltage to Z133 and is not low voltage to Cal/OSHA.
Z133 anticipates this and yields. Section 4.3.2.1.1 states: "When the low voltage safety regulations of an individual OSHA state plan require it, voltages below 750 V shall be utilized." The Annex A definition of the Level 2 Arborist says the same thing at more length. So in California the Level 2 ceiling is 600 volts by the standard's own instruction, and the distance owed between 600 and 750 volts comes from Title 8, not from Table 2.
None of which makes a Z133 Electrical Level a California credential. Title 8 has its own defined terms, a qualified tree worker under section 3420(b) and a qualified line clearance tree trimmer under section 2700, and neither is defined by reference to Z133. A card that says Electrical Level 3 Arborist proves what the employer assessed. It does not answer the question a Cal/OSHA inspector asks, which is whether this person meets the Title 8 definition for the work being done.
Where Z133 bites, in OSHA's own words
The clearest statement of what a voluntary standard does and does not do is in OSHA's June 24, 2021 enforcement guidance for tree care and tree removal operations, the memorandum that cancelled the 2008 tree care citation directive. It names Z133 three times and reaches a different result each time.
It creates a safe harbor. On anchorage for climbers, the memo says that where the compliance officer finds the inspector of the anchor point meets the definition of qualified person "and the employer otherwise follows the requirements of ANSI Z133-2017, § 8.1.11, no citation shall be issued." Following the consensus standard is the abatement.
It refuses one. On hoisting a worker with a crane, the memo notes that 29 CFR 1910.180(h)(3)(v) prohibits it, that Z133-2017 section 5.7.11 allows it with conditions, and then: "An employer's reliance on the ANSI standard is not a defense to a violation of § 1910.180(h)(3)(v)." Where a regulation and the consensus standard conflict, the regulation wins and Z133 is not an excuse.
And it makes Z133 the yardstick where no regulation exists. On hand and portable powered tools, the memo tells compliance officers considering General Duty Clause citations to "examine ANSI B175.1-2012 ... as well as ANSI Z133-2017, Safety Requirements for Arboricultural Operations." It then tells them to "consider whether the recommendations contained in those consensus standards are consistent with OSHA's standards, interpretations and policies." That is the General Duty Clause route: Z133 is evidence that the industry recognized the hazard and that a feasible means of abatement existed.
California adopts Z133 exactly once, and not in the electrical article. A note to section 3427(b)(10), on palm frond skirts, cites "the ANSI Z133.1-2006 standard 'Arboricultural Operations - Safety Requirements' Section 8.2.7." That is a note rather than a requirement, in the palm subsection, naming an edition three revisions out of date. Cal/OSHA's own Tree Work Safety Guide does not mention Z133 at all.
The fourth route is the one that decides most days of actual work: the contract. Utility master service agreements and training programs routinely require Z133 conformance by name. ACRT's 40 hour Line Clearance Arborist Certification course lists "Current ANSI Z133 Safety Standards" among its subjects. When a specification says Z133 without an edition year, "current" now means 2026, and the crew working to a 2017 copy is out of conformance with a document nobody has told them changed.
What Z133 requires you to keep, and what it only recommends
Read carefully, Z133 imposes almost no recordkeeping obligation and one real annual one.
The recordkeeping is advisory. Section 3.7.4: "Employee training and retraining should be documented." Section 3.7.5.1: "On-the-job assessments should be documented." Section 3.4.3.4, on job briefings: "The job briefing should be documented." All three are should. Annex B, which recommends that training documentation be retained for the duration of employment, is informative and not part of the standard at all. A program that keeps no training file is not violating Z133.
The annual obligation is mandatory, and it sits in all three qualified-level subsections. Sections 4.3.5, 4.4.5 and 4.5.5 each require the employer to determine, "through inspections conducted on at least an annual basis, that the arborist is complying with the safety-related work practices required by this section." Not that the arborist was trained once. That the arborist is complying, checked at least yearly, by observation. Section 3.7.5 repeats it for every employee regardless of electrical level.
That is the one Z133 item an evaluator can ask for by date. A file of completion certificates answers the training question. It does not answer whether the employer performed the annual field assessment, which needs a date, an observer, a person observed, and what was watched. What an individual qualification file has to show beyond that is set by Title 8 and 1910.269, not by Z133.
What is still unsettled and who decides it
Three things are open, and it is worth being honest about which.
OSHA's safe harbor now points at text that no longer exists. The 2021 memo conditions its no-citation policy on the employer following "ANSI Z133-2017, § 8.1.11," which required the climber to visually inspect the anchor point from the ground and "subject it to a load approximately twice the weight of the climber before climbing commences."
In the 2026 edition, section 8.1.11 is about load-rated screw links. The anchor point requirement is now section 8.2.11, and it requires only that the arborist "visually inspect the condition of the anchor point from the ground."
The load test is gone, replaced by a pointer to Annex C.4, which is informative. An employer following the current edition is not following the 2017 text the memo names. Whether the safe harbor still applies is not answered anywhere in OSHA's published material. The body that decides is OSHA's Directorate of Enforcement Programs, which the same memo already designates as the point of contact on tree care feasibility questions, and in a state plan state the answer may come from the state first.
Z133's own glossary still uses the retired term. Section 4.5 renamed the role to Electrical Level 4 Arborist, but the Annex A definition of "line clearance" still describes work "performed by qualified line-clearance arborists or qualified line-clearance arborist trainees." The old and new vocabulary are both live in the same document. For a contract that has to name a role, the safe course is to name the section number and the level together, and to state the edition year.
There is still no federal tree care standard. OSHA's Tree Care Operations rulemaking has been open since an Advanced Notice of Proposed Rulemaking on September 15, 2008, with a stakeholder meeting in 2016 and Small Business Advocacy Review Panel teleconferences in April and May 2020.
The agency's own page still says "The next step in the rulemaking process is to publish a proposed rule." Until that rule exists, the General Duty Clause and Z133 do the work a standard would do, which is precisely why the edition on your truck and the edition in your contract need to be the same one.
Further reading
Table 1 of 8 CCR 2950: the minimum approach distance, and who owes it: California's own approach distance table, which is the enforceable one and does not match Z133's.
Qualified line clearance tree trimmer versus qualified tree worker: The two Title 8 credentials Z133's Electrical Levels do not map onto.
OSHA 1910.269(r): the three qualification tiers: The federal tiers Z133's Level 4 says it is equivalent to, and the altitude arithmetic behind Table 4.
Frequently asked questions
Is ANSI Z133 the law?
No. Z133 is a voluntary consensus standard published by the International Society of Arboriculture under an Accredited Standards Committee, and section 1.2 says it is intended as a guide to federal, state, and local authorities in drafting their regulations and may be adopted in whole or in part. It becomes enforceable in three ways: when a jurisdiction adopts a piece of it, when it is written into a contract, and when OSHA uses it as evidence of a recognized hazard under Section 5(a)(1) of the OSH Act. OSHA's June 24, 2021 tree care enforcement guidance tells compliance officers to examine ANSI Z133-2017 when considering General Duty Clause citations.
What edition of ANSI Z133 is current?
ANSI Z133-2026, Safety and Health Requirements for Arboricultural Operations, available from ISA as of May 27, 2026. It replaces ANSI Z133-2017, which ANSI approved on October 5, 2017. The 2026 edition also changed the title: the standard was formerly Safety Requirements for Arboricultural Operations, and before 2012 it was designated ANSI Z133.1. Earlier revisions ran in 1978, 1982, 1987, 1994, 2000, 2006, 2012, and 2017.
What is the minimum approach distance to a 12 kV line under ANSI Z133-2026?
It depends which of the four tables you read. An Electrical Level 1 Arborist owes 10 feet under Table 1. An Electrical Level 2 Arborist, qualified only to 750 volts, also owes 10 feet, because 12 kV is above that level's ceiling. An Electrical Level 3 Arborist owes 2 feet 10 inches under Table 3. An Electrical Level 4 line clearance arborist owes 2 feet 3 inches under Table 4 at sea level. Same span, same conductor, four different numbers.
Does ANSI Z133-2026 still use the term incidental line clearance?
Not in its section headings. Sections 4.3 and 4.4, which define the Electrical Level 2 and Level 3 Arborists, each carry a note reading Formerly: Incidental Line Clearance, and the Annex A definitions of both levels still describe the hazards associated with incidental line clearance. The phrase survives as a cross-reference rather than as the name of a category.
Can a Level 2 or Level 3 Arborist work closer than 10 feet to a 12 kV conductor in California?
Not on Z133's authority. Section 4.3.2.1.1 says that when an OSHA state plan's low voltage regulations require it, voltages below 750 volts shall be used, and California's own line clearance article draws its low voltage exception at 600 volts. More importantly, Z133 is not the enforceable rule in California. Title 8 section 2950 Table 1 is, and it owes 10 feet on a 12 kV circuit to anyone who is not a qualified line clearance tree trimmer or trainee.
