Gas Safe CCN1 Core Prep: Free Mock Test & Practice Questions

Q: Why do people fail the Gas Safe CCN1 Core Prep?

Common reasons: Confusing 'immediately dangerous' vs. 'at risk' situations (GIUSP) Figures checked October 2026.

Gas Safe CCN1 Core Prep

Core domestic gas safety (ACS CCN1) revision questions.

Written against the published specification.

Pass mark 30/40 60 minutes Gas Safe/ACS How many can I get wrong?

About this practice. Revision Robin is built and maintained by Bloor Engineering Ltd, a UK-registered company. Our Gas Safe CCN1 Core Prep questions are written and reviewed in-house to match the current syllabus, each with a plain-English worked explanation. They are original practice material, not the official exam questions and not affiliated with or endorsed by Gas Safe/ACS. Always confirm current test rules, fees and content with the official provider. See our Terms and Privacy.

Sit a full mock under the clock at least once. Nerves are half the battle.

Free practice questions

Try 3 real Gas Safe CCN1 Core Prep questions

Have a go, then reveal the worked explanation. A taster from a bank of 219 original questions. Unlock for unlimited drills and full timed mocks.

Q1. Under the Gas Safety (Installation and Use) Regulations 1998 (GSIUR), who is legally responsible for ensuring that any gas appliance, fitting, flue or pipework they install is safe?

A. The installer who carries out the work
B. The householder who commissioned the work
C. The gas supplier delivering to the property
D. The local authority building control officer

Show answer & explanation

✓ Answer: A. The installer who carries out the work

GSIUR places the duty on the person carrying out the installation work to ensure it is done safely and left in a safe condition. The householder has separate landlord-type duties only if they are also a landlord; the gas supplier and building control have no role in installation safety under GSIUR.

Q2. Why is carbon monoxide particularly dangerous compared with many other combustion products?

A. It is heavier than air and only collects at floor level
B. It has a strong smell that is easily detected before harm occurs
C. It is highly flammable at very low concentrations in air
D. It is colourless, odourless and binds to haemoglobin more readily than oxygen

Show answer & explanation

✓ Answer: D. It is colourless, odourless and binds to haemoglobin more readily than oxygen

Carbon monoxide has no colour, taste or smell, so victims are often unaware of exposure. It binds to haemoglobin around 200-300 times more readily than oxygen, forming carboxyhaemoglobin and starving the body of oxygen, which is why undetected exposure is so dangerous.

Q3. During a let-by test, the installation is isolated at the emergency control valve. What result indicates the ECV itself may be letting by?

A. The pressure continues to rise after isolation
B. The pressure remains completely static after isolation
C. The pressure falls sharply and continues to fall
D. The gauge reading drops to zero instantly

Show answer & explanation

✓ Answer: A. The pressure continues to rise after isolation

If pressure continues to rise after the ECV has been closed and the downstream side isolated, this shows gas is still passing through the closed valve, indicating the ECV itself is letting by rather than the fault lying in the customer's pipework. A static reading after isolation would instead suggest the downstream pipework is sound.

Exam mode

Full mock exam

40 random questions, real timing, marked against the official pass mark. Different every time.

The first 8 of 40 questions are free, with your score on them. Finishing the paper, your result against the pass mark and every answer explained come with the paid version.

Practice material only. This is revision practice, not official training, assessment or certification, and not a substitute for the required course or supervised experience. Always confirm the current requirements with the official awarding body or test provider before relying on it.

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Topic drills

Ten quick questions on one topic, marked instantly with explanations.

1 free drill left.

Who has to sit the Gas Safe CCN1 Core Prep

Who needs a Gas Safe CCN1 Core Prep?

All engineers working on domestic gas appliances in the UK, Isle of Man, and Guernsey to register with Gas Safe.

The real Gas Safe CCN1 Core Prep: format

What is the Gas Safe CCN1 Core Prep pass mark?

Real exam pass mark: Each subject area must be passed; theory components typically require around 80%. Our mock marks you at 30 out of 40, the threshold we mark against.

What it costs, and what a resit costs

How much does the Gas Safe CCN1 Core Prep cost?

Rebooking after a fail: Reassessment can be taken up to 6 months before expiry or no more than 12 months after expiry. If past 12 months, initial assessment is required.

How hard is it

What is the Gas Safe CCN1 Core Prep pass rate?

Real exam first-time pass rate: One provider claims a 100% pass rate for new entrants and 99% for qualified engineers. Another states a 99.9% pass rate. Difficulty: Theory is generally considered not difficult, often open-book, but practical assessments are seen as the hardest part.

Why people fail it

Why do people fail the Gas Safe CCN1 Core Prep?

Confusing 'immediately dangerous' vs. 'at risk' situations (GIUSP).

Figures for the real exam from vertexaisearch.cloud.google.com, checked October 2026. Fees and rules change, so confirm with the test provider before you book.

Gas Safe CCN1 Core Prep: common questions

Frequently asked

How many questions are in the Gas Safe CCN1 Core Prep?

The exam has 40 questions. Every Revision Robin mock uses the same 40-question format so your practice matches the real thing.

How long do you get?

The test is timed at 60 minutes. Our full mock runs on the same clock so you can practise your pacing.

Are these the real exam questions?

No. Our questions are original and written to match the current syllabus, so they give realistic practice without copying the official paper. Every answer comes with a plain-English explanation. Always confirm current rules and content with Gas Safe/ACS.