The useful starting point
Define the control's intended function, identify its dependencies, and match the evidence to a specific possible failure.
Describe the intended function
The fictional workshop wants learners to use the current instruction sheet during training. Its proposed safeguard is a single approved document page linked by a QR code on each training station. The intended function is not “have a QR code.” It is “make the applicable current sheet available at the point of use.”
CCOHS recommends reviewing whether controls remain effective. In this case, begin by stating the intended function precisely. That gives you a basis for asking how the safeguard could fail to perform it.
Follow the dependencies in the story
The QR code must point to the right page. The page must display the approved version. The device must open it, and the learner must be able to recognize which station the sheet applies to. These are dependencies of this fictional design, not a universal technology checklist.
Now imagine the page works perfectly but displays last month's approved version. A successful page load would prove only access, not currency. Conversely, a current document on an inaccessible page does not fulfill the whole intended function either.
Write the failure-mode table
| Possible failure in the example | Effect on the intended function | Evidence question |
|---|---|---|
| Code points to another station's sheet | Information is available but inapplicable | Does the identifier match? |
| Page retains an older approved revision | Applicable information may be outdated | Which revision was approved for use? |
| Device cannot open the page | Information is not available there | What does the access check show? |
| Printed copy conflicts with the page | Users encounter competing instructions | How is the applicable version established? |
Separate failure possibility from observed failure
The table lists ways the fictional safeguard could fail. It does not claim those failures have happened. A study answer should label each item as a possibility until the supplied evidence establishes an actual condition.
If a photograph shows the code on the station, you can say the code was present. You cannot conclude that its destination, revision and usability were checked. If the question supplies a test confirming the correct page and revision on one station, keep the conclusion to that tested scope rather than extending it automatically to every station.
Choose a test that matches the claim
The learner's first proposal is to count QR stickers. That answers a presence question. A second proposal compares station identity, destination and approved revision in the supplied training records. That addresses more of the intended function.
The lesson is not to add unlimited checks. Select evidence that could reveal the particular failure being considered. If the concern is revision accuracy, another photograph of the sticker adds little. Finish by writing one sentence stating what has been checked and one stating the remaining uncertainty. This makes control reasoning precise without turning a classroom example into a technical specification.
Check your reasoning.
Every training station has a QR sticker. Does that prove every station provides its applicable current instruction sheet?
Open the suggested reasoning
No. Sticker presence does not establish the destination, station match, approved revision or access. Those are separate dependencies of the fictional safeguard.
An original learning exercise from NCSO Prep, not an official exam question.
Sources and scope
Source review: . The examples and study methods are NCSO Prep editorial material. Official requirements and workplace decisions must be checked against the applicable current source.
- CCOHS: Hierarchy of Controls
Background on reviewing controls and unintended hazards. Reviewed October 18, 2026.