How to Improve Safety with Six Sigma Quality Improvement

Six Sigma is normally associated with reducing defects, process variation and production costs. However, the same structured problem-solving approach can also strengthen industrial safety when it is integrated with an established occupational health and safety system.

The need is significant. U.S. private-sector employers reported 2.5 million nonfatal workplace injuries and illnesses in 2024. Manufacturing accounted for approximately 332,600 cases, with a rate of 2.7 cases per 100 full-time workers.

Six Sigma cannot replace risk assessments, machine-safety requirements, regulatory compliance or ISO 45001. What it can do is make safety improvement more systematic, measurable and sustainable.

How Six Sigma Supports Workplace Safety

At the center of Six Sigma is DMAIC: Define, Measure, Analyze, Improve and Control. ASQ describes DMAIC as a data-driven strategy for improving existing processes.

For safety teams, the “defect” being investigated might instead be an unsafe condition, excessive exposure, equipment failure, near miss or weakness in a safety-critical process.

Key Safety Practices and Standards

1. Define a Specific Safety Problem

Avoid broad objectives such as “reduce accidents.”

A stronger Six Sigma project might investigate:

• repeated hand injuries around a press operation;
• forklift/pedestrian near misses in one warehouse zone;
• frequent machine-guard bypasses;
• excessive manual lifting in packaging;
• unusually high corrective-action closure times.

Defining a narrow process boundary makes data collection and root-cause analysis much more useful.

Operators should participate at this stage. OSHA notes that workers often know the most about hazards associated with their jobs and recommends involving them in identifying and improving safety conditions.

2. Measure More Than Accident Numbers

A common mistake is using only recordable injuries as the safety KPI.

Those are lagging indicators—they describe something that has already happened.

OSHA recommends using both leading and lagging indicators.

The measurement system also needs consistent definitions. If one department reports every near miss while another reports almost none, comparing their raw numbers may lead to incorrect conclusions.

3. Analyze the Root Cause, Not Just Worker Behavior

Suppose operators repeatedly reach into a machine to remove jammed material.

Writing “operator failed to follow procedure” may describe the event without explaining why it keeps happening.

A Six Sigma team should investigate questions such as:

• Why does the material jam?
• Does machine setup vary between shifts?
• Is guarding difficult to use?
• Does production pressure encourage bypassing?
• Is preventive maintenance being completed?
• Can the operation be redesigned so access is unnecessary?

Tools such as Pareto charts can prioritize recurring problems, while fishbone diagrams and the 5 Whys help structure root-cause investigation.

FMEA is particularly useful for proactive safety work. ASQ describes Failure Mode and Effects Analysis as a systematic method for identifying potential failures, examining their consequences and prioritizing actions to reduce risk.

4. Improve the Process Using the Hierarchy of Controls

Finding the root cause is only valuable when it leads to effective controls.

NIOSH recommends considering controls in this preferred order:

1. Elimination
2. Substitution
3. Engineering controls
4. Administrative controls
5. Personal protective equipment

Elimination, substitution and engineering controls generally provide stronger protection because they depend less on continuous worker action.

For example, if operators are exposed to a rotating component, installing an engineered interlocked guard is generally a stronger solution than relying only on warning signs and retraining.

This is where Six Sigma and safety engineering work particularly well together: DMAIC identifies why variation or failure occurs, while the hierarchy of controls guides how the hazard should be reduced.

5. Control the Improvement

Safety improvements often fail when attention moves to the next project.

The Control phase prevents that.

Consider monitoring:

• overdue corrective actions;
• machine-guard inspection compliance;
• preventive-maintenance completion;
• exposure levels;
• safety-critical process parameters;
• recurring near-miss categories.

Control charts can be helpful where safety performance depends on continuously measured process variables. ASQ notes that control charts help determine whether process variation remains stable or whether unusual, special-cause variation has appeared.

For example, unexpected variation in pressure, temperature, machine vibration or another validated safety-critical parameter can trigger investigation before equipment failure develops.

Six Sigma Safety vs Traditional Reactive Safety

The objective is not to generate more statistics. It is to use evidence to identify where the process is allowing hazardous conditions to develop.

Common Mistakes to Avoid

Organizations should avoid:

• treating every injury simply as a Six Sigma “defect”;
• relying only on injury-rate reductions;
• assuming low incident counts mean low risk;
• using FMEA scores as the only basis for safety decisions;
• jumping directly to PPE or retraining;
• ignoring worker observations;
• closing DMAIC projects without monitoring the new controls.

Six Sigma should complement—not override—applicable safety regulations, engineering standards, risk assessments and occupational safety management systems such as ISO 45001. ISO describes ISO 45001 as a framework for managing OH&S risks and improving occupational health and safety performance.

Conclusion

Six Sigma quality improvement can make workplace safety more systematic by turning recurring safety problems into measurable process-improvement projects.

The most effective approach is straightforward:

The real value of Six Sigma in safety is therefore not achieving a statistical “sigma level” for accidents. It is creating a disciplined method for detecting process weaknesses, eliminating causes and preventing hazardous conditions from returning.

When DMAIC, worker participation, FMEA, leading indicators, statistical process control and the hierarchy of controls are used together, safety improvement becomes part of continuous operational improvement rather than simply a reaction to the latest incident.