Process Safety

Our experts deliver end-to-end process safety services that help clients identify, evaluate, and mitigate risks in complex operating environments. Our experience spans multiple industries—including chemical and pharmaceutical, oil and gas, clean energy (hydrogen, carbon capture and storage, and energy from waste, utilities, aerospace manufacturing, and defence—as well as partnerships with design system integrators, engineering procurement and construction firms (EPCs), and end users.

Our comprehensive service offering combines deep regulatory knowledge with advanced technical tools, such as quantitative risk assessment (QRA) and consequence modelling. Through our Leading with Science® approach, we deliver process insights that enable safer operations, reduce liabilities, and optimise performance while maintaining appropriate and robust layers of protection.

Hazard Studies

Tetra Tech provides independent facilitation, chairing, and action tracking for all six stages of hazard studies—from concept and design to operations (five-yearly reviews) and decommissioning—to ensure rigorous assessment and mitigation of process-related risks.

• Hazard identification (HAZID)
• Hazard and operability study (HAZOP) – IEC 61882
• Computer HAZOP (CHAZOP)
• ‘What if’ technique, structured what if technique (SWIFT), process hazard analysis (PHA), process hazard review (PHR)
• Bowtie analysis
• Layers of protection analysis (LOPA)
• Safety Integrity Level (SIL)
• Specialist support including human factors, Fire Engineering, and Radiological

Functional Safety

We provide safety lifecycle services that extend from hazard studies through the functional safety lifecycle, ensuring compliance with standards and achievement of tolerable risk.

• Compliance with IEC 61508 and IEC 61511
• Instrumented safety system design and SIL verification (achieved random hardware failures, systematic capability and architectural assessments)
• Functional safety lifecycle management, supporting functional safety management procedures, safety requirement specifications (SRS) and proof test procedures
• Functional safety assessments (all five stages)
• Combined functional safety technical and human factors assessments on proof test and operational procedures

Machinery Safety

We support the assessment of machinery systems to ensure compliance with harmonised, designated safety standards and legislation.

• Compliance with IEC 61508, IEC 62061 and ISO 13849, plus relevant type B and type C standards
• Safety system design and verification (SIL and performance level (PL))
• Provision and Use of Work Equipment Regulations (PUWER) and machinery risk assessments (ISO 12100, ISO 13849)
• Machinery Directive technical file development (CE and UKCA marking)
• Essential health and safety requirements (EHSRs)

Consequence Modelling and QRA

Our specialists provide advanced modelling to support informed, risk-based decision-making. We select the most appropriate tool for the clients requirements. We have extensive experience in both phenomenological, empirical and computational fluid dynamics (CFD) including PHAST, FLACS, KFX, FDS.

• Dispersion (flammable, toxic and asphyxiation), fire, and explosion modelling
• Individual and societal risk quantification
• Fire and gas detector mapping (BS 60080)
• Control of major accident hazards (COMAH) predictive assessments
• Modelling to support design accident loads for active and passive fire protection, and explosion

Explosive Atmospheres – ATEX / DSEAR Consultancy

Our experts support clients to meet legal obligations under Atmosphères Explosibles (ATEX) and Dangerous Substances and Explosive Atmospheres Regulations (DSEAR). We provide consultancy services on gases, vapours, mists (IEC 60079-10-1) and combustible dusts and powders (IEC 60079-10-2).

• DSEAR risk assessment (explosion protection documents (EPD))
• Hazardous area classification (HAC) studies and drawings (for example, Energy Institute Guide 15 (EI15) and IGEM/SR/25)
• Ignition hazard assessment (EN 1127-1: electrical, mechanical, RFI, static, and other sources)

COMAH and Offshore Safety Case

Tetra Tech assists clients in developing legally compliant submissions under the Control of Major Accident Hazards (COMAH) Regulations and offshore safety legislation.

• Hazardous substance consent
• COMAH threshold reviews for dangerous substance inventories (lower tier and upper tier)
• Safety report and safety case development
• Hazard identification and risk evaluation
• Occupied building risk assessment (OBRA)
• Regulator liaison and submission support
• ALARP (as low as reasonably practicable) demonstration
• Human factors

Human Factors

Our human factors team enhances safety by systematically analysing the interaction between people, systems and environments. We ensure that tasks, equipment, and processes are compatible with users’ physical and psychological capabilities, minimising the potential for human error and supporting optimal performance.

• Human factors and ergonomics assessment reports
• Human factors integration plan (HFIP)
• Human error identification
• Safety critical task analysis (SCTA), tabular task analysis (TTA), hierarchical task analysis (HTA), and task walk-down or talk-through
• Quantitative and qualitative human reliability analysis (HRA) and derivation of human error probabilities (HEPs)
• Assessment of performance influencing factors (PIFs)
• HF design input including control systems and human-machine interfaces, main control room layout, alarm handling and prioritisation, equipment, workspaces, safe systems of work, procedures and instructions, and environmental ergonomics
• Allocation of function between the operator and the system tasks
• Behavioural safety and safety culture assessments
• Human factors support for training programmes, competency, and processes
• Independent peer reviews
• Regulator liaison