Machine Guarding Compliance: A Standards Reference for the US and Canada

How machine guarding law is structured

Machine guarding in both countries is governed by performance-based law. The rules mandate an outcome, that workers are protected from moving parts and other hazards, and they stop there. They do not hand you a design, approve a guard in advance, or certify one after the fact. That single fact explains most of the confusion in this field, and it is why guarding quality varies so widely from one site to the next.

It helps to picture the rules in two layers.

The first layer applies to every workplace. Wherever a worker shares space with moving machinery, a packaging line, a conveyor, a press, a robotic cell, or the rotating equipment in an elevator machine room, a worker-safety regulator requires the hazards to be guarded. In the United States that is OSHA and the state OSH plans, acting under 29 CFR 1910.212. In Canada it is the provincial ministries of labour, acting under provincial occupational health and safety regulations such as Ontario's Regulation 851. This layer is the subject of part one below, and it is where citations for unguarded equipment come from.

The second layer applies only to certain equipment. Some classes of equipment carry their own product-safety code on top of the general duty, enforced by a separate regulator. Conveyors carry ASME B20.1. Elevators carry the elevator safety code, ASME A17.1 in the US and CSA B44 in Canada, enforced by state and municipal authorities having jurisdiction in the US and by bodies such as TSSA in Ontario. For an elevator machine room, both layers apply at once, which is the subject of part two.

These layers operate of their own force. Worker-safety law reaches the equipment as a workplace hazard regardless of any product code. The elevator code, for its part, defers outward where another code governs an aspect of the installation: it routes electrical working space to the electrical codes, NFPA 70 in the US and CSA C22.1 in Canada, rather than restating them. In Ontario the elevator regulator has written the connection down, requiring through its alteration order that added machine guarding conform to the elevator code's equipment-guarding and clearance provisions.

The practical consequence, especially in an elevator machine room, is that guarding accepted by one regulator is not automatically acceptable to the other. A barrier that satisfies the labor inspector but encroaches on a code-required working clearance will fail, and a code-compliant layout that leaves a sheave exposed will be cited. Compliant guarding answers to every layer that applies.

A note on editions. Throughout this Guide, a standard's current published edition is identified. The edition published is not always the edition enforced where you are. Adoption happens jurisdiction by jurisdiction, and a state, province, or city can enforce an earlier edition for years after a newer one is published. Confirm the adopted edition with your local jurisdiction before you design to a specific clause number.

The US-to-Canada standards cross-walk

The standards that govern machine guarding line up across the two countries in recognizable pairs. No competitor in this niche lays them out side by side. The table below maps each layer of the safeguarding picture from the US instrument to its Canadian counterpart. The first three rows apply to every workplace; the last two are the added layer for elevators.

The pairs are counterparts, not identical twins. The US relies on a federal worker-safety statute backed by consensus standards from ANSI; Canada relies on provincial regulations backed by CSA standards. They reach the same place by different routes. The sections that follow take each instrument in turn.

PART ONE — Standards that apply to every workplace

Whatever the equipment is, a bagging line, a conveyor, a press brake, a robotic cell, or the traction machine and rope drives in an elevator machine room, guarding it is governed first by the general machine-guarding standards below. They treat the equipment as a workplace hazard and apply in every US state and Canadian province. For how these apply to a specific line, see the industrial equipment guarding page; for how they apply to elevator equipment, see part two and the elevator machine room guarding guide.

OSHA 29 CFR 1910.212

What it is. The general machine-guarding requirement under US federal occupational safety law, found in Subpart O of 29 CFR Part 1910. It is the standard OSHA cites most often when a machine's moving parts are left exposed in a US workplace.

What it requires, at a principle level. It calls for one or more methods of guarding to protect operators and other workers from hazards such as point of operation, ingoing nip points, rotating parts, and flying chips and sparks. Where possible, the guard is affixed to the machine, and it is designed so that no part of a worker's body can reach into the danger zone during operation. The standard names the outcome and leaves the design to the employer, which is why the performance standards below exist to fill in the how.

Current status. In force, with stable text. There is no edition cycle in the consensus-standard sense; the regulatory text is amended through federal rulemaking.

Who enforces it. Federal OSHA, or a state OSH plan in states that run their own. Citations and penalties for unguarded equipment originate here.

Canadian counterpart. There is no single federal equivalent. The duty lives in provincial OHS regulations instead, such as Ontario's Regulation 851, Sections 24 and 25.

ANSI B11.19

What it is. The US consensus standard that defines how risk-reduction measures, including guards and other safeguarding devices, must perform. Where OSHA 1910.212 says guarding is required, B11.19 supplies the engineering criteria a guard is measured against.

What it requires, at a principle level. It governs guard construction, the size of openings in a guard, and the reach-through distances that pair an opening size with the distance to the hazard behind it. The governing principle is that the closer a guard sits to the hazard, the smaller its permitted openings. It also addresses other safeguarding methods, such as presence-sensing devices, and the conditions under which each is appropriate.

Current status. ANSI B11.19-2019, reaffirmed in 2024 and carried as B11.19-2019 (R2024).

Who enforces it. B11.19 is a voluntary consensus standard, not a regulation. It carries weight because OSHA can cite it as evidence of recognized industry practice under the General Duty Clause, and because it is the criteria set engineers and inspectors reach for when judging whether a guard is adequate.

Canadian counterpart. CSA Z432, covered next.

CSA Z432

What it is. The Canadian safeguarding-of-machinery standard, the counterpart to ANSI B11.19. It sets out how machine safeguarding is to be designed and applied in Canada.

What it requires, at a principle level. Like B11.19, it covers guard construction, opening sizes, and reach distances, along with the hierarchy of safeguarding methods and the role of risk assessment in selecting among them. The same reach-through logic applies: opening size is tied to distance from the hazard.

Current status. CSA Z432:23, the fourth edition, which supersedes the 2016 edition.

Who enforces it. Z432 is referenced and given force through provincial OHS regulations and through inspectors and engineers who apply it as the recognized standard of practice. A province's OHS regulation is the legal hook; Z432 is the technical content.

US counterpart. ANSI B11.19, above.

The Ontario and provincial OHS framework

The worker-safety duty in Canada lives in provincial regulation. Ontario is treated here in the most detail because its framework is the clearest and the most explicit about connecting worker-safety law to equipment codes; every other province has an equivalent structure with its own instruments.

The guarding duty. Ontario's Regulation 851 under the Occupational Health and Safety Act is the provincial machine-guarding regulation. Sections 24 and 25 require exposed moving parts and in-running nip hazards to be guarded. Sections 75 and 76 add that maintenance and repair happen only with motion stopped and the equipment blocked or locked out. This is the Ontario equivalent of the OSHA 1910.212 duty.

A vocabulary note that trips people up. Two similar acronyms refer to entirely different things, and they are routinely confused, including across the border:

PSR stands for Pre-Start Health and Safety Review, an Ontario requirement under O. Reg. 851 Section 7, in which a professional engineer reviews certain apparatus, structures, or protective elements before they are first put into service in a factory. It is an Ontario worker-safety concept.

PSSR stands for Pre-Startup Safety Review, a US requirement under OSHA's Process Safety Management standard, 29 CFR 1910.119(i), which applies to processes involving highly hazardous chemicals.

They are not the same review, they sit under different laws in different countries, and a requirement triggered under one says nothing about the other. PSR is named here as reference vocabulary a buyer may encounter; confirm whether any review applies to your project with the appropriate professional.

Code editions, adoption, and review requirements vary by province and by US state. Confirm the rules in force with your local jurisdiction.

PART TWO — Elevator machine room compliance

Everything in part one applies to an elevator machine room, because the machine room is a workplace and its traction machine, sheaves, ropes, brake, governors, and controllers are exactly the kind of moving and energized equipment the general standards govern. Elevators then carry one more layer on top: the elevator safety code, and a second regulator to enforce it.

ASME A17.1 / CSA B44

What it is. The elevator safety code. ASME A17.1 in the United States and CSA B44 in Canada are published jointly as one harmonized binational code. It governs the elevator itself, including the equipment-guarding provisions for machine rooms and machinery spaces, the maintenance clearances around equipment, and what counts as an alteration when guarding is added. Conveyors have an analogous sector standard in ASME B20.1; for elevators, this is that standard.

What it requires, at a principle level. The code names which elevator components must be guarded, such as driving-machine sheaves and ropes, exposed gears and sprockets, and projecting keys and screws on shafts. It sets maintenance-clearance requirements, including a clear path to components that require maintenance. And it defers outward for electrical working space, routing that to the electrical codes. The code governs the elevator; it does not replace the worker-safety law from part one that also reaches the machine room.

Current status. The edition in force on a given unit is the one the local jurisdiction has adopted, not necessarily the newest published. Ontario currently adopts ASME A17.1-2019 / CSA B44:19 through Code Adoption Document Amendment 295/22, in effect since August 2022. A newer harmonized edition, A17.1:2025 / CSA B44:2025, was published on January 30, 2026 and is scheduled to come into force on February 1, 2027. Even then it governs a given installation only where the authority having jurisdiction has adopted it. A published edition is not an enforced one until a jurisdiction takes that step, and as of mid-2026 Ontario has not, so A17.1-2019 / CSA B44:19 remains the code in force here.

Who enforces it. State and municipal authorities having jurisdiction in the US; TSSA in Ontario and equivalent bodies in other provinces.

Specific clause numbers depend on the adopted edition and are addressed in context on the elevator machine room guarding guide.

The two regulators in an elevator machine room

The single most common point of confusion in this niche is that two separate regulators have jurisdiction in every machine room, and neither will do the other's job.

The worker-safety regulator, OSHA and the state OSH plans in the US, provincial ministries of labour in Canada, enforces the guarding duty from part one and issues the citations for unguarded equipment.

The elevator safety authority, state and municipal AHJs in the US, TSSA in Ontario, enforces the elevator code and the rules for altering an elevator. Adding machine guarding to an existing elevator touches this regulator. In Ontario, adding guarding is a defined alteration, filed with TSSA as a design submission and installed by a registered elevator contractor using certified elevating devices mechanics, or under their direct supervision. TSSA's live alteration instrument is Director's Order 296/22, which carries forward the equipment-guarding, clearance, and working-space requirements that added guarding has to meet. US jurisdictions apply their own alteration and permit rules.

There is one more constraint that guarding routinely violates when nobody checks: the electrical working space in front of disconnects and live controller faces. The elevator code routes this to the electrical codes. NEC Table 110.26(A)(1) starts at 3 ft of clear depth in the US and rises with voltage and conditions; in Ontario it is 1000 mm under the Ontario Electrical Safety Code, the value TSSA's alteration order applies to guarding in front of control equipment. A screen erected inside that envelope fails even if every moving part is covered.

For the component-by-component method of guarding each piece of equipment in the room, drive machine, brake, governors, selector, rope gripper, hydraulic units, and the rest, see the elevator machine room guarding guide, the modern successor to the 2009 Ontario best-practices guideline MRG has hosted since publication.

Fall protection on the car top

Machine room equipment guarding protects workers from moving parts. The other guarding obligation on the same units is fall protection on top of the car, governed through the adopted edition of ASME A17.1 / CSA B44 and jurisdictional retrofit requirements. The code calls for a standard railing on every side of the car top where a 300 mm (12 in.) ball can pass between the car-top edge and the hoistway enclosure, and on sides with no hoistway enclosure at all. In Ontario, the retrofit wave began with TSSA Director's Order 245/10, with requirements since carried forward in the Code Adoption Document.

MRG car top rail options

The letter of conformity

When MRG guarding is engineered and fabricated, the design basis can be documented. A letter of conformity, available on request, identifies the standards the guarding was designed to meet, such as OSHA 29 CFR 1910.212, ANSI B11.19, CSA Z432, and, for elevator work, the applicable elevator code provisions.

It helps to be precise about what this letter is and is not.

What it is. A statement of the standards and code provisions the guarding was designed against, tied to the engineering drawings produced for the project. It gives an owner, a contractor, or a consultant a clear, written design basis to put in the building's records and to show an inspector who asks what the guarding was built to.

What it does not do. It does not perform or replace the risk assessment for the installation. It does not certify the elevator, the building, or the overall workplace as compliant, and it does not substitute for the jurisdiction's own inspection and acceptance. MRG does not perform the risk assessment; that responsibility belongs to the customer or contractor, who knows the equipment, the space, and the way it is maintained.

The substantive engineering work lives in the drawings produced from survey. The letter is the plain-language companion to those drawings: a trust signal and a record, available on request, not a regulatory certificate.

For how a project moves from survey to documented guarding, see MRG Component Guarding, the industrial equipment guarding page, and the elevator machine room guarding guide.

Send us the project.

Tell us the equipment, the space, and the jurisdiction, and we will engineer guarding designed to the worker-safety law and any applicable equipment code at once, fabricate it in our own shop, and document the design basis. Installation services are available depending on project scope and location, across the United States and Canada.

Frequently asked questions

Which standards govern machine guarding in the US and Canada?

For any workplace, the general standards apply first: in the United States, OSHA 29 CFR 1910.212 sets the legal duty to guard and ANSI B11.19 supplies the performance criteria; in Canada, provincial occupational health and safety regulations set the duty and CSA Z432 supplies the performance criteria. For elevators, the harmonized elevator code, ASME A17.1 in the US and CSA B44 in Canada, adds equipment-specific guarding and clearance requirements on top.

What is the difference between OSHA 1910.212 and ANSI B11.19?

OSHA 1910.212 is the law: it requires guarding and is the standard OSHA cites for unguarded equipment. ANSI B11.19 is a voluntary consensus standard that defines how a guard must perform, including opening sizes and reach-through distances. The law requires guarding; the consensus standard says what good guarding looks like, and OSHA can point to it as recognized practice.

What is the Canadian equivalent of ANSI B11.19?

CSA Z432, currently the Z432:23 edition. It is the Canadian safeguarding-of-machinery standard and covers the same ground as B11.19: guard construction, opening sizes, and reach distances. It is given legal force through provincial OHS regulations.

Do the same standards apply to industrial equipment and to elevator machine rooms?

The general machine-guarding standards apply to both, because an elevator machine room is a workplace like any other. Elevators carry an additional layer that industrial equipment does not: the elevator safety code, ASME A17.1 / CSA B44, enforced by a separate regulator, with its own guarding, clearance, and alteration rules.

Which edition of ASME A17.1 / CSA B44 is in force?

The edition your jurisdiction has adopted, which is not always the newest published. Ontario currently adopts ASME A17.1-2019 / CSA B44:19 through Code Adoption Document Amendment 295/22, in effect since August 2022. A newer edition, A17.1:2025 / CSA B44:2025, was published in January 2026 and is scheduled to come into force on February 1, 2027, but only where the authority having jurisdiction adopts it. Until a jurisdiction takes that step, the edition it already adopted is the one that governs. Confirm the adopted edition with your local authority.

Who enforces machine guarding requirements?

For general guarding, the worker-safety regulator: OSHA and state OSH plans in the US, provincial ministries of labour in Canada. For elevators, a second regulator also applies: the elevator safety authority, state and municipal AHJs in the US and TSSA in Ontario, which enforces the elevator code and its alteration rules. Compliant guarding satisfies every regulator that applies, and none of them will design it for you.

What is the difference between a PSR and a PSSR?

They are different reviews under different laws. A PSR, Pre-Start Health and Safety Review, is an Ontario requirement under O. Reg. 851 Section 7, in which a professional engineer reviews certain apparatus or protective elements before they are first put into service. A PSSR, Pre-Startup Safety Review, is a US requirement under OSHA's Process Safety Management standard, 29 CFR 1910.119(i), for processes involving highly hazardous chemicals. A requirement under one says nothing about the other.

Does MRG perform the risk assessment?

No. The risk assessment is the responsibility of the customer or contractor, who knows the equipment, the space, and how it is maintained. MRG engineers and fabricates guarding to the assessed hazards and the applicable standards, and can provide a letter of conformity, available on request, documenting the design basis.

What is a letter of conformity, and what does it certify?

It is a written statement of the standards and code provisions the guarding was designed to meet, tied to the project's engineering drawings, available on request. It documents the design basis for an owner's records and for an inspector. It does not perform the risk assessment, certify the elevator or building as compliant, or replace the jurisdiction's inspection and acceptance.

Does the 2009 Ontario Best Practices Guideline still apply?

It was never law, and it predates several editions of the current codes, but its component-by-component method remains sound. MRG hosts the original document for reference. The elevator machine room guarding guide on this site carries that method forward against current US and Canadian requirements.