Critical to Safety requirements are based on the safety concerns of customers. These might include industry safety standards and workplace health and safety (OH&S) rules.

CTS Requirements vs. Drivers

Like other CTX requirements, Critical to Safety requirements are typically based on customer drivers. These are customer needs that can be translated into one or more requirements. Drivers are customer-focused, whereas CTS requirements state what needs to be done internally to meet those drivers.

Examples of Customer Drivers

Some common safety-related customer drivers are:

  • Toys for babies must not include small, hard parts that might be choking hazards.
  • A worker must be able to use an industrial machine without bending or stooping awkwardly.
  • Packages for delivery must not exceed 30 pounds in weight.

If not met, all of these drivers could negatively impact the end customer or people in the supply chain.

Examples of Critical to Safety Requirements

We can use the customer drivers mentioned above to create example CTS requirements:

  • Make all toy parts from fabric, no hard plastics.
  • Minimum machine bench height of 4′.
  • You can package multiple order items in the same box as long as the combined weight of items, box, and padding does not exceed 30 pounds.


Critical to Safety requirements often overlap Critical to Quality. In fact, you’ll find that some companies treat CTS as a subset of CTQ. However, it’s often useful to instead separate them into two different sets of requirements.

The main reason you should separate the two is that safety issues aren’t always strictly quality issues. You can manufacture a product that passes all quality tests but is still considered unsafe. One of the best examples of this is in baby toys. A stuffed toy might meet all quality guidelines: its seams are firmly and evenly stitched, its fabric is closely and uniformly woven, and its eyes are sewn on carefully. However, it might fail its safety requirements for children under the age of two because its eyes could choke the child if torn off and put in the mouth.

Developing Critical To Safety Requirements

Your first step in developing CTS requirements is to look for drivers. You can find these by:

  • Talking to customers.
  • Researching industry safety standards.
  • Looking at federal safety laws that might apply to you.
  • Checking supplier requirements.
  • Asking about workplace health and safety regulations that might apply to your customers.

You can then use a variation on the CTQ tree to create your CTS requirements.

Points to remember

When developing CTS requirements, make sure that they fit these criteria:

  • Actionable: Staff is able to follow the requirement.
  • Measurable: You can measure the result objectively.
  • Clear: Everyone understands the CTS requirement.
  • Achievable: Staff can meet the requirement without undue pressure.

Example Critical To Safety Six Sigma Projects

Some Six Sigma projects focus on CTS improvements, such as the ones below:

  • Modularizing a desk’s design so that consumers can customize the leg length.
  • Implementing new government regulations for a product.
  • Researching and documenting OH&S rules for a new market.


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