PSR Triggers for HAZOPs: Understanding When Pre-Start Health & Safety Reviews Are Required for Process Safety
Posted by HITE Engineering • July 2025
In Ontario’s industrial sector, Pre-Start Health and Safety Reviews (PSRs) are a cornerstone of workplace safety compliance. While PSRs are commonly associated with machine guarding or racking systems, they are equally critical — and legally required — in complex process environments, particularly in environments where HAZOPs (Hazard and Operability Studies) are conducted.
If your facility involves chemical processes, flammable substances, or hazardous energy, you may be legally obligated to complete a PSR in tandem with or following a HAZOP. Failure to understand the triggers can lead to regulatory violations, fines, or serious safety risks. Being able to identify these requirements as early as possible will often save on costly downtime and expensive redesign work.
This article explains how PSR requirements intersect with HAZOPs, what triggers a review, and how to ensure you’re compliant with Ontario Regulation 851 under the Occupational Health and Safety Act (OHSA).
🧠 What Is a HAZOP?
A HAZOP (Hazard and Operability Study) is a structured, team-based risk assessment method used to identify potential hazards and operability issues in process systems, especially in chemical, pharmaceutical, or energy-related industries.
HAZOPs:
- Analyze what could go wrong in a process (e.g., overpressure, leaks, ignition)
- Examine the causes, consequences, and safeguards in place
- Are often required for new or modified process systems
- Help ensure the process design aligns with safety objectives and that overall risk is mitigated sufficiently
While HAZOPs are voluntary in many jurisdictions, they’re considered best practice and are often required by internal corporate policy or insurance providers.
📌 When Does a HAZOP Intersect with a Trigger a PSR?
In Ontario, a PSR is legally required if a new or modified process involves any of the eight scenarios listed in Section 7 of Regulation 851.
For processes typically requiring a HAZOP-relevant processes, these are the most common typical PSR triggers are:
Item 1 – The Use or Storage or Dispensing of Flammable or Combustible Liquids
If your process the facility is expected to store or dispense significant quantities of flammable liquids such as involves solvents, paints, fuelsfuels, or vapour-producing substances, a PSR is mandatory.
Examples:
- Solvent recovery systems
- Batch reactors using ethanol or acetone
- Indoor fuel storagePaint manufacturing
Item 2 – Machine Safeguarding
If your process includes machinery guarding with interlocks, safety control systems, or mechanical guarding that could exposesafeguarding devices that are implemented to protect workers to from injury, a PSR is required.
Examples:
- Centrifuges Mixers with locking lids
-
Blenders Manufacturing equipment with interlocked access doors
Item 4 – Processes Involving a Risk of Ignition or Explosion
This is a broad trigger relevant to many processes where ignitable concentrations of dusts, vapours, mists, or fibers may be present industries. If your HAZOP identifies processes involving fine dustsheat sources, oxidizers, flammable vapours, gases, or heated ignition points chemicals, a PSR compliance assessment is likely needed.
Item 5 – Dust Collection Systems
A PSR is required when combustible dust is collected or handled, especially where a risk of explosion or deflagration potential exists.
Examples:
- Spray boothsFood manufacturing involving flour or sugar
- Grinding or sanding lines processing wood, metal, or plastic
-
Silo unloading operations involving fine dust
Item 8 – Use Exposure of Personnel toof Designated Substances
If the process involves a risk of exposing personnel to hazardous levels of chemicals and substances listed as designated substances (e.g., benzene, isocyanates, lead, suspended particulates), and a ventilation system is used as the protective mechanism, a PSR is would be triggered under this item.
⚖️ What the Law Says
Under Ontario Regulation 851, employers must complete a PSR before a process or equipment is put into use, if it falls under one of the triggering categories and the relevant listed provisions apply.
The review must be conducted or approved by a Professional Engineer (P.Eng.), and the resulting report must:
- Identify non-compliance with applicable codes (e.g., CSA, NFPA, TSSA, etc.)
- Recommend measures to bring the process into compliance
- Be retained on-site and made available to inspectors and workers
Importantly, HAZOPs are not a substitute for a PSR. While a HAZOP identifies potential areas of risk scenarios that might help identify when a PSR would be applicable, a HAZOP study is completed by a multidisciplinary team of individually with broad expertise. o Only a licensed engineer can provide the technical assessment required when a PSR is identified as being applicableverify code compliance and sign off on the PSR.
🧪 HAZOP vs PSR: How They Work Together
Think of the HAZOP as a hazard identification tool, and the PSR as a technical legal compliance review.
| Aspect | HAZOP | PSR |
|---|---|---|
| Purpose | Identify process hazards | Verify code/legal compliance |
| Conducted by | Multidisciplinary team | Professional Engineer (P.Eng.) |
| Methodology | Brainstorming, guide words | Technical inspection + code analysis |
| Required by Law? | Not in Ontario (best practice) | Yes, under Regulation 851 if triggered |
| Output | Risk register, action items | Engineer-sealed report |
🏠 Real-World Examples of HAZOP-Driven PSRs
-
Pharma Plant
Modifies a solvent mixing station to increase capacity. HAZOP flags the risk of vapour ignition and presence of flammable materials.
➡️ PSR Triggered Under: Item 1 & Item 4-
Flammable liquids used in process
-
Risk of vapour ignition from heat or equipment
Paint Manufacturer
Installs a new ventilation system for a ‘small batch’ area where paints are mixed and tested for quality control dust collection system for spray booths. Possible present of Ccombustible dust and overspray flammable vapours are identified.
➡️ PSR Triggered Under: Item 4 & Item 5-
Explosion risk from overspray ignition
-
Dust collection system involving combustible particles
Lab Facility
Adds a compressed gas manifold system. HAZOP identifies leaks, overpressure, and potential reactivity.
➡️ PSR Triggered Under: Item 8 and potentially Item 4-
Use ofPossibility of personnel exposure to a hazardous designated substances (toxic or reactive gases)
-
Potential explosion/ignition scenario from gas system
-
🛠️ How HITE Engineering Helps
At HITE Engineering, we specialize in both HAZOP facilitation and PSR compliance.
We offer:
- Review of HAZOP outputs to determine PSR triggers
- On-site inspections and code reviews by licensed engineers (O. Reg. 851, OFC< OBC)
- Explosion protection design assessments (CSA, NFPA 33, 34, 68, 68/69, 652)
- Process equipment guarding evaluations (CSA Z432, Z460)
- Signed and sealed PSR reports for MLITSD compliance
If your facility is planning a process change, chemical upgrade, or new equipment installation, we’ll help you avoid compliance gaps and ensure safety from the start.
📞 Book a PSR for Your Process Upgrade
Don’t wait until the Ministry shows up — proactively identify if your HAZOP requires a PSR. Contact our engineering team or visit our Pre-Start Health & Safety Review page for more info.
✅ FAQ: PSRs and HAZOP Triggers
Does every HAZOP require a PSR in Ontario?
No. A PSR is only required if the process falls under one of the eight triggers in Section 7 of Regulation 851. Many HAZOP-identified risks often do.
What are the most common PSR triggers in process safety?
Typical Triggers include machine safeguarding, flammable liquids, combustible dust, explosion hazards, machine safeguarding, and exposure to designated substanceslifting devices.
Can a HAZOP replace a PSR?
No. A HAZOP is a risk analysis method. A PSR is a legal technical engineering review and must be performed by a P.Eng. if triggered by law.
Who can perform a PSR after a HAZOP?
Only a licensed Professional Engineer (P.Eng.) in Ontario can perform or approve a PSR. Exception can be made for Item 8 PSRs, but The report PSR reports are typically required to be must be signed and sealed.
Do PSRs apply outside Ontario?
PSRs are specific to Ontario’s Regulation 851. Other provinces may have similar engineering review and compliance requirements, but not identical rules.
