Critical to Safety (CTS): How to Establish Safer Processes

Critical to Safety (CTS) requirements sit at the heart of any responsible Lean Six Sigma initiative. They define the features, conditions, and controls that protect people, assets, and the environment. While many teams focus on quality, cost, or delivery, safety must never take a back seat. In fact, strong CTS management often drives better performance across all other dimensions.

This guide explains CTS in a clear, practical way. You will learn what CTS means, why it matters, how to identify it, and how to manage it using Lean Six Sigma tools. You will also see real examples, structured tables, and actionable methods you can apply immediately.

What Are Critical to Safety (CTS) Requirements?

Critical to Safety (CTS) requirements describe the conditions that must exist in a process to prevent harm. These requirements focus on eliminating hazards, reducing risks, and ensuring safe operation.

Unlike Critical to Quality (CTQ), which focuses on customer satisfaction, CTS focuses on protecting:

• Employees
• Customers
• Equipment
• The environment

In simple terms, CTS answers this question:

“What must go right to keep people safe?”

Why CTS Matters in Six Sigma

Safety is not optional. It directly impacts business performance.

First, unsafe processes create risk. Injuries, environmental damage, and equipment failures can stop operations.

Next, safety incidents increase costs. These include medical expenses, downtime, legal fees, and regulatory penalties.

Moreover, poor safety performance damages reputation. Customers and stakeholders lose trust quickly.

Finally, strong safety systems improve efficiency. Stable processes produce fewer defects and less variation.

Key Benefits of CTS

Benefit	Description	Impact
Risk Reduction	Identifies and eliminates hazards	Fewer incidents
Cost Savings	Avoids injury-related costs	Higher profitability
Compliance	Meets regulatory requirements	Lower legal risk
Process Stability	Reduces variability	Better quality
Employee Morale	Creates a safe workplace	Higher engagement

CTS vs CTQ vs CTC

Lean Six Sigma uses multiple “critical to” categories. Each serves a different purpose.

Category	Focus	Key Question
CTS (Critical to Safety)	Safety and risk	Is it safe?
CTQ (Critical to Quality)	Customer satisfaction	Does it meet expectations?
CTC (Critical to Cost)	Financial efficiency	Is it cost-effective?

Although they differ, they often overlap. For example, a machine guard (CTS) also prevents defects (CTQ) and reduces downtime (CTC).

Characteristics of Strong CTS Requirements

Effective CTS requirements share several traits.

First, they are measurable. Vague statements create confusion.

Next, they are specific. Each requirement targets a clear risk.

Also, they are actionable. Teams can design controls around them.

Finally, they are enforceable. Audits and monitoring ensure compliance.

Examples of Good vs Poor CTS

Type	Example	Issue
Poor	“Ensure safe operation”	Too vague
Better	“Operator must wear cut-resistant gloves during operation”	Clear and actionable
Best	“Operator must wear ANSI level 4 cut-resistant gloves at all times during blade operation”	Specific and measurable

How to Identify CTS Requirements

Identifying CTS starts with understanding risk. You must analyze the process step by step.

Step 1: Map the Process

Start with a process map or value stream map. Break the process into steps.

Step 2: Identify Hazards

Look for anything that could cause harm.

Examples include:

• Moving machinery
• High temperatures
• Chemical exposure
• Electrical systems

Step 3: Assess Risk

Evaluate both severity and likelihood.

Step 4: Define CTS Requirements

Convert risks into specific safety requirements.

Step 5: Validate with Stakeholders

Engage operators, engineers, and safety experts.

CTS Identification Tools

Several Lean Six Sigma tools help identify CTS requirements.

Common Tools

Tool	Purpose	CTS Application
Process Mapping	Visualize workflow	Identify hazard points
FMEA (Failure Modes and Effects Analysis)	Assess risk	Rank safety risks
Hazard Analysis	Identify dangers	Define safety controls
Root Cause Analysis	Find causes of incidents	Prevent recurrence
Control Charts	Monitor stability	Detect unsafe variation

Using FMEA for CTS

Failure Modes and Effects Analysis (FMEA) is one of the most powerful tools for CTS.

It helps you identify failure modes and assess risk using:

• Severity (S)
• Occurrence (O)
• Detection (D)

You then calculate the Risk Priority Number (RPN).

Example FMEA for CTS

Process Step	Failure Mode	Effect	Severity	Cause	Occurrence	Detection	RPN	CTS Action
Cutting	Blade exposure	Injury	10	Missing guard	4	3	120	Install interlocked guard
Heating	Overheating	Burns	9	Sensor failure	3	4	108	Add temperature alarm

Translating CTS into Measurable Metrics

Once you identify CTS requirements, you must measure them.

Examples of CTS Metrics

Requirement	Metric	Target
Machine guarding	% compliance	100%
PPE usage	Audit score	≥ 98%
Temperature control	Max temp deviation	±2°C
Chemical exposure	ppm level	Below OSHA limit

Metrics ensure accountability. They also allow continuous improvement.

Integrating CTS into DMAIC

Lean Six Sigma uses the DMAIC framework. CTS fits into every phase.

Define Phase

Identify safety requirements and risks.

Measure Phase

Collect safety data. Track incidents and near misses.

Analyze Phase

Find root causes of safety issues.

Improve Phase

Implement controls and eliminate hazards.

Control Phase

Monitor safety performance and sustain gains.

CTS in the Define Phase

During Define, teams clarify safety expectations.

Key Activities

• Identify stakeholders
• Define safety goals
• Capture Voice of the Customer (VOC) for safety

Example

A manufacturing plant defines a goal:

“Reduce hand injuries by 50% within 6 months.”

CTS in the Measure Phase

Next, teams gather data.

Key Metrics

• Injury rate
• Near-miss frequency
• PPE compliance

Example Table

Metric	Current Value	Target
Injury rate	4 per month	2 per month
PPE compliance	92%	100%

CTS in the Analyze Phase

Now, teams identify root causes.

Common Techniques

• Fishbone diagrams
• 5 Whys
• Pareto analysis

Example

Problem: Frequent hand injuries

Root Cause: Lack of proper guarding

CTS in the Improve Phase

Teams implement solutions.

Common Improvements

• Install safety guards
• Add automation
• Improve training
• Introduce error-proofing

Example

Before: Manual cutting process
After: Automated cutting with interlocked guard

CTS in the Control Phase

Finally, teams sustain improvements.

Control Methods

• Audits
• Visual controls
• Standard work
• Training programs

Example Control Plan

Control	Frequency	Owner
PPE audit	Daily	Supervisor
Machine inspection	Weekly	Maintenance

Real-World CTS Examples

Manufacturing Example

A plant experiences frequent burns during a heating process.

CTS Requirement

Temperature must not exceed 200°C.

Solution

• Install temperature sensors
• Add automatic shutoff

Result

Burn incidents drop to zero.

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Healthcare Example

A hospital faces medication errors.

CTS Requirement

Correct dosage must be administered every time.

Solution

• Barcode scanning system
• Double-check procedures

Result

Error rate drops significantly.

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Construction Example

Workers face fall hazards.

CTS Requirement

Workers must use fall protection above 6 feet.

Solution

• Harness systems
• Safety training

Result

Fall incidents decrease sharply.

Common CTS Mistakes

Many organizations struggle with CTS.

Frequent Issues

• Vague requirements
• Lack of measurement
• Poor enforcement
• Ignoring near misses

How to Avoid Them

Mistake	Solution
Vague CTS	Define measurable criteria
No tracking	Implement metrics
Weak controls	Use audits and automation
Reactive approach	Focus on prevention

Role of Leadership in CTS

Leadership drives safety culture.

Strong leaders:

• Prioritize safety
• Allocate resources
• Hold teams accountable

Without leadership support, CTS efforts fail.

Building a Safety Culture with CTS

CTS supports a proactive safety culture.

Key Elements

• Employee involvement
• Continuous training
• Open communication
• Accountability

Example

A company encourages workers to report near misses. As a result, it identifies risks early and prevents incidents.

CTS and Regulatory Compliance

Many industries must follow strict regulations.

Examples include:

• OSHA standards
• Environmental regulations
• Industry-specific guidelines

CTS helps ensure compliance by translating regulations into actionable requirements.

CTS and Risk Management

Critical to Safety requirements play a central role in risk management.

Risk Equation

Risk = Severity × Probability

CTS reduces both factors.

• It lowers severity through safeguards
• It reduces probability through controls

Advanced CTS Techniques

Organizations can go beyond basic CTS.

Error Proofing (Poka-Yoke)

Design systems that prevent mistakes.

Automation

Reduce human exposure to hazards.

Predictive Analytics

Use data to predict safety risks

Example: CTS in a Chemical Process

Scenario

A plant handles hazardous chemicals.

CTS Requirements

Requirement	Control
Exposure limit	Ventilation system
Spill prevention	Containment barriers
Emergency response	Alarm system

Outcome

The plant reduces incidents and improves compliance.

Linking CTS to Business Performance

Safety drives performance.

Impact Areas

Area	Effect
Productivity	Less downtime
Quality	Fewer defects
Cost	Lower incident costs
Reputation	Stronger brand

CTS Dashboard Example

A dashboard helps track safety performance.

Sample Metrics

Metric	Value	Status
Injury rate	1/month	Good
Near misses	5/month	Monitor
PPE compliance	99%	Excellent

Best Practices for Managing CTS

Follow these proven practices.

Key Practices

• Define clear requirements
• Use data-driven decisions
• Engage employees
• Monitor continuously
• Improve proactively

Step-by-Step CTS Implementation Plan

Step 1: Assess Current State

Step 2: Identify Risks

Step 3: Define CTS Requirements

Step 4: Implement Controls

Step 5: Monitor Performance

Step 6: Continuously Improve

Conclusion

Critical to Safety (CTS) requirements form the foundation of safe, high-performing processes. They protect people, reduce risk, and improve business outcomes.

When you define clear CTS requirements, measure performance, and enforce controls, you create a safer workplace. At the same time, you boost efficiency, quality, and profitability.

Lean Six Sigma gives you the tools. However, success depends on execution. Focus on prevention. Use data. Engage your team. Most importantly, treat safety as a core value, not a priority that can shift.

By doing so, you will not only meet safety requirements—you will build a culture where safety drives excellence.