The CompEx pass mark for the written assessment is 70%. This applies to all units — Ex01, Ex02, Ex03, Ex04, and Ex05. The practical assessment is assessed on a pass/fail basis by a CompEx assessor.
Written Assessment Structure
The written assessment consists of multiple choice and short answer questions covering the knowledge requirements for the unit. A score of 70% or above is required to pass. There is no negative marking — unanswered questions score zero.
Practical Assessment
The practical assessment is a demonstration of competency observed by an accredited CompEx assessor. For inspection units (Ex03/Ex04) you will be required to carry out a structured inspection of Ex equipment and correctly identify and classify deficiencies. For installation units (Ex01/Ex02) you will install and connect Ex equipment to a defined specification. The assessor will observe your methods, decisions, and the outcome.
A 70% pass mark means you can afford to lose marks on approximately 30% of questions. However, in practice, the questions that carry the most marks tend to be the application questions — deficiency classification, equipment selection, standard identification — rather than straightforward recall questions. Strong preparation in applied decision-making gives you the best chance of a comfortable pass.
What Happens if You Fail?
If you fail the written assessment you can resit after a waiting period specified by JTL. If you fail the practical assessment, the assessor will advise on the areas where additional competency development is required before reassessment. Many candidates find that focused preparation on their weak areas — particularly deficiency classification and equipment selection — makes a significant difference on reassessment.
How Are Marks Distributed Across Topics?
The written assessment doesn't weight every topic equally. Based on the structure of the units, expect proportionally more questions on the areas that carry the greatest safety significance — deficiency classification (Category X, A, B, C), correct protection type selection for a given zone and gas group, and cable gland/entry requirements. Pure recall questions (e.g. "what does T4 mean") tend to be a smaller proportion than application questions that require you to combine several pieces of knowledge to reach a correct decision.
Resit Waiting Periods
JTL specifies a minimum waiting period before a resit is permitted — this exists to ensure candidates use the time to genuinely address knowledge gaps rather than simply retaking the same assessment immediately. The exact waiting period can vary, so check directly with your assessment centre or JTL for the current policy applicable to your unit. Use any waiting period productively: review the specific areas where you lost marks if your centre provides that feedback, and focus revision there rather than re-covering material you already know well.
Does a Narrow Pass or Fail Matter?
No — CompEx certification doesn't record or care whether you passed at 71% or 98%. Once you've achieved the 70% threshold, you hold the same valid certificate as anyone else who passed. There's no advantage to aiming higher than 70% beyond the personal confidence and safety margin it gives you. That said, candidates who pass comfortably above 70% rather than right at the boundary often report feeling more prepared for the practical assessment too, since the underlying knowledge that gets you a strong written score is the same knowledge the practical assessment draws on.
While 70% is technically all you need, exam-day factors — nerves, an unfamiliar phrasing of a question, simple misreads — can cost a few percentage points versus your true underlying knowledge. Preparing to a standard well above 70% in practice gives you a buffer against an off day, rather than leaving your pass entirely dependent on a perfect performance.