Change Analysis

1. Why Change Analysis Matters

One of the oldest truths in safety engineering is that most incidents are preceded by a change. A new chemical is substituted, a shift schedule is altered, a guard is removed for maintenance, a vendor delivers a slightly different part, a crew member is replaced by a less experienced worker, or a procedure is rewritten. Each of these introduces hazards that were not present when the original system was designed, evaluated and controlled. Change analysis is the structured method safety professionals use to find those hazards before they cause harm, and to understand them after an incident has occurred.

For the ASP exam, change analysis sits inside the Safety Programs and Concepts domain alongside other hazard analysis techniques (Job Hazard Analysis, What-If, FMEA, Fault Tree Analysis, HAZOP). You are expected to know what it is, when it is the most appropriate tool, how it differs from the other techniques, and how it is embedded in formal Management of Change (MOC) programs such as the one required by OSHA's Process Safety Management standard (29 CFR 1910.119(l)). Questions in this area are common because the concept bridges proactive hazard control, regulatory compliance and incident investigation.

2. What Change Analysis Is

Definition: Change analysis is a hazard analysis technique that compares a baseline (a known, accepted, previously analyzed or accident-free condition) with a new or proposed condition, identifies every difference between the two, and then evaluates each difference for its potential to create new hazards or defeat existing controls.

The underlying logic is simple: if the baseline was safe and the new situation is not, the cause must lie in what is different. Rather than re-analyzing an entire system from scratch, change analysis focuses attention on the deltas.

Change analysis has two main applications you must be able to distinguish:

• Proactive (pre-change) application: Used as the analytical heart of a Management of Change program. Before a change is implemented, the analyst asks: what is being changed, what could that change affect, and what new controls or reviews are needed? This is forward-looking hazard identification.

• Reactive (post-incident) application: Used in accident investigation, most notably within the MORT (Management Oversight and Risk Tree) methodology developed by the U.S. Department of Energy and in Kepner-Tregoe problem analysis. The investigator compares the situation at the time of the incident with a comparable situation in which no incident occurred and isolates the changes that contributed.

3. Categories of Change

Exam questions often test whether you recognize the breadth of what counts as a change. Change analysis considers differences in:

• People: new or temporary workers, staffing reductions, loss of experienced personnel, changes in supervision, fatigue, training gaps.
• Equipment and tools: new machinery, modifications, substitutions, aging or wear, different vendors, software and control-system updates.
• Materials: new raw materials, different grades or concentrations, changes in packaging, substitutes that behave differently.
• Procedures and methods: revised work instructions, shortcuts, deviations, changes in sequence or timing.
• Environment: weather, lighting, noise, temperature, housekeeping, layout changes, new adjacent operations.
• Organization and management: reorganizations, mergers, contractor use, production pressure, budget cuts, policy shifts, changes in ownership.

Changes may also be classified as planned vs. unplanned, permanent vs. temporary, intentional vs. unintentional and gradual (creeping) vs. sudden. A critical exam point: temporary changes and gradual drift still require analysis. Many major incidents (Flixborough is the classic example) resulted from temporary modifications that were never formally evaluated.

4. How Change Analysis Works – Step by Step

Step 1 – Define the situation or problem. State clearly what change is proposed (proactive) or what incident occurred (reactive).

Step 2 – Describe the baseline. Document the comparable condition: the original design basis, the last approved configuration, the normal operating procedure, or a similar operation that ran without incident. The quality of the baseline determines the quality of the analysis.

Step 3 – Describe the new or incident situation. Capture the same attributes (who, what, where, when, how, with what) so the two situations can be compared item by item.

Step 4 – Compare and list every difference. Use a structured worksheet or a change analysis form with the categories above (people, equipment, materials, procedures, environment, management). Be exhaustive; small or indirect differences are frequently the significant ones.

Step 5 – Analyze each difference for effect. For each change ask: Does this introduce a new hazard? Does it increase the probability or severity of an existing hazard? Does it bypass, degrade or remove an existing barrier or control? Could it affect something downstream or in an adjacent system?

Step 6 – Integrate the findings. In proactive use, specify controls, training, procedure updates, drawing revisions and approvals required before the change proceeds. In reactive use, feed the significant changes into the broader causal analysis (root cause, barrier analysis, events and causal factors charting) and develop corrective actions.

Step 7 – Verify, communicate and close out. Ensure affected employees are informed and trained, documents reflect the as-built condition, a pre-startup safety review is conducted where required, and the change is formally authorized.

5. Change Analysis Within Management of Change (MOC)

A formal MOC program institutionalizes change analysis. Key elements, drawn heavily from OSHA PSM 1910.119(l) and ANSI/ASSP Z10, include:

• A written procedure that defines what constitutes a change and who may authorize one.
• A documented technical basis for the change.
• An analysis of the impact on safety and health.
• Modifications to operating procedures and training.
• Defined time period for temporary changes, with a required return to the original condition or formal conversion to a permanent change.
• Authorization and approval signatures.
• Updating of process safety information (drawings, P&IDs, material data).
• Communication to and training of affected employees and contractors before start-up.
• A Pre-Startup Safety Review (PSSR) for changes significant enough to require updated process safety information.

Replacement in kind: A frequently tested concept. Replacing a component with an identical item that meets the original design specification is not a change and does not trigger MOC. Anything that deviates from the design specification (different material, rating, size, manufacturer with different characteristics, a software version with changed logic) is a change and must be analyzed. Exam questions like to present a scenario that looks like replacement in kind but actually involves a specification difference.

6. Change Analysis in Accident Investigation

In investigation, change analysis answers the question: what was different this time? The investigator identifies a comparable accident-free situation (the same task on a previous day, the same machine before modification, the same crew under normal staffing) and systematically compares it with the accident situation. Differences such as a substituted worker, a new lubricant, a missing guard, overtime fatigue or a rushed schedule are then evaluated for causal significance.

Change analysis is rarely used alone in investigations. It is typically combined with barrier analysis (what barriers failed or were missing) and events and causal factors analysis (the sequence of events). Within MORT, change analysis and barrier analysis are the two primary analytical tools. Remember that change analysis identifies what was different; it does not by itself prove causation, which is why it feeds a broader root cause process.

7. Strengths and Limitations

Strengths: Simple, quick, requires no specialized software, highly effective at catching hazards introduced by modifications, applicable to both hardware and organizational issues, and excellent for focusing a review on the areas of highest risk rather than re-analyzing an entire system.

Limitations: Entirely dependent on an accurate baseline; cannot detect hazards that were present in the baseline all along; tends to miss gradual or unrecognized changes if nobody flags them; and does not quantify risk. For complex systems it is usually paired with HAZOP, FMEA or fault tree analysis.

8. Distinguishing Change Analysis From Other Techniques

• Job Hazard Analysis (JHA/JSA): Breaks a task into steps and identifies hazards at each step. Not comparative.
• What-If Analysis: Brainstorming of hypothetical failure questions. Broad and unstructured compared with change analysis.
• FMEA: Examines each component for its failure modes and effects. Inductive, bottom-up, component-focused.
• Fault Tree Analysis: Deductive, top-down, starts with an undesired top event and uses logic gates. Can be quantitative.
• HAZOP: Uses guide words (no, more, less, reverse, other than) applied to process parameters in a team setting. Deviation-based but built around process nodes rather than a before/after comparison.
• Energy Trace and Barrier Analysis: Follows energy flows and the barriers that control them.
• Change Analysis: The only technique whose defining feature is a before-and-after comparison against a baseline.

If a question emphasizes comparison, differences, deviations from a known safe condition, modifications, substitutions or 'what changed,' the answer is change analysis.

9. Exam Tips: Answering Questions on Change Analysis

Tip 1 – Look for the trigger words. Baseline, comparable accident-free situation, difference, deviation, modification, substitution, 'what changed,' MOC, replacement in kind, temporary change. Any of these should immediately point you toward change analysis.

Tip 2 – Know the two applications. If the stem is about a proposed modification, think MOC and proactive hazard identification. If the stem is about an incident that already happened and asks you to compare with a prior successful operation, think change analysis as an investigation tool (MORT, Kepner-Tregoe).

Tip 3 – Master replacement in kind. The exam loves scenarios where a part is replaced. Ask yourself: does the replacement meet the original design specification exactly? If yes, no MOC. If anything differs (material, pressure rating, manufacturer characteristics, size, software logic), MOC is required. Do not be fooled by phrases such as 'similar' or 'equivalent' – only identical-to-specification counts as in kind.

Tip 4 – Temporary does not mean exempt. Temporary changes, bypasses, jumpers and trial runs require the same analysis as permanent changes, plus a defined time limit and a plan to return to the original state.

Tip 5 – Remember that people and organizations are changes too. Staff reductions, reorganizations, new supervisors, contractor use and schedule changes fall within change analysis and MOC. Questions that present an organizational change and ask which hazard analysis tool applies are testing this point.

Tip 6 – Know the PSM MOC elements. Be able to list the technical basis, impact on safety and health, modifications to procedures, time period for temporary changes, authorization requirements, employee notification and training, and updating of process safety information. Also know that a PSSR is required when a change results in modified process safety information.

Tip 7 – Pair it correctly. If a question asks which two techniques are central to MORT investigations, the answer is change analysis and barrier analysis. If asked which analysis best supplements change analysis to establish causation, think root cause analysis or events and causal factors analysis.

Tip 8 – Eliminate by defining feature. When choices include JHA, FMEA, FTA, HAZOP, What-If and change analysis, mentally tag each with its defining feature (task steps, component failure modes, top-down logic tree, guide words, brainstorming, before-and-after comparison). Match the stem to the feature and the distractors fall away.

Tip 9 – Watch for the baseline trap. A question may ask about the biggest weakness of change analysis. The correct answer usually relates to its dependence on an accurate, well-documented baseline and its inability to find hazards that existed in the original condition.

Tip 10 – Think like the exam writer. BCSP questions favor the best or most appropriate answer. Change analysis is the best answer when a system was previously evaluated and something has been or will be altered. It is not the best answer for the initial hazard analysis of a brand-new process (that is HAZOP, What-If or FMEA territory) or for analyzing the steps of a routine task (JHA).

10. Quick Review Summary

• Change analysis compares a baseline to a new or incident condition and evaluates each difference for hazard potential.
• It is used proactively in Management of Change and reactively in accident investigation (MORT, Kepner-Tregoe).
• Categories of change: people, equipment, materials, procedures, environment, organization; planned or unplanned; temporary or permanent; sudden or gradual.
• Replacement in kind is not a change; anything deviating from design specification is.
• OSHA PSM 1910.119(l) requires written MOC procedures addressing technical basis, safety and health impact, procedure modifications, time limits for temporary changes, authorization, training and updated process safety information, with a PSSR where applicable.
• Strength: simple and focused. Weakness: depends on the baseline and cannot find pre-existing hazards.
• Trigger words on the exam: baseline, comparison, difference, modification, substitution, what changed.