CCN1 exam questions and answers: free practice and mock tests

What CCN1 questions are really testing

The best CCN1 questions are rarely trivia. They usually test whether you understand the safe boundary of domestic gas work: when to test, when to isolate, when to warn, when a result is not acceptable and when an appliance or installation cannot be left in use.

• Scope: what the certificate and registered category actually allow.
• Evidence: which check proves the installation, appliance or flue is safe enough to continue.
• Sequence: what has to happen before gas is restored or an appliance is relit.
• Assessment: whether a situation is ID or AR, or a safe standards shortfall recorded separately.
• Units and readings: gas rate, pressure, ventilation free area and CO/CO2 ratio.

How to review an answer

After every practice question, write one short sentence explaining why the correct answer is safest. Then write one sentence explaining why the tempting wrong answer fails. That turns multiple choice into active recall instead of pattern matching.

1. Name the risk: gas escape, CO, poor combustion, inadequate air, wrong scope or unsafe operation.
2. Name the proof: tightness test, flue/spillage evidence, gas rate, analyser reading, visual inspection or documentation.
3. Name the action: continue, stop, isolate, label, notify, repair, retest or escalate.
4. Check whether the question is asking for first action, best action, legal boundary or final result.

Five original CCN1 practice checks

• Question: A room has an open-flued appliance and a covered permanent air vent. Answer: treat the air supply as inadequate until restored; a closable window is not permanent ventilation.
• Question: The meter control is shut but pressure still rises during the let-by check. Answer: do not continue with a normal tightness-test judgement until the passing control issue is handled.
• Question: A gas fire passes a calm-room spillage check but fails when the cooker hood runs. Answer: the fan effect matters; follow the unsafe-situations route and do not ignore the failure.
• Question: A boiler gas rate is close to the data plate but the CO/CO2 ratio is above the allowed limit. Answer: the gas rate does not override unsafe combustion evidence.
• Question: A customer refuses permission to disconnect an immediately dangerous appliance. Answer: follow the current unsafe-situations procedure, warning notice and escalation route; do not leave it as a casual advisory note.

The biggest wrong-answer patterns

• Choosing a convenience action, such as opening a window, instead of correcting a permanent safety requirement.
• Treating a visible flame or a lit appliance as proof that combustion and flueing are safe.
• Jumping to appliance repair before proving the installation and controls are safe.
• Using a CO alarm as if it replaces servicing, flue checks or analyser evidence.
• Memorising one pressure, timing or limit without checking which gas type, installation or standard the question describes.

When to switch from reading to practice

Once you can explain a topic in your own words, try CCN1 practice questions before reading the explanation. Work out the safe action or calculation yourself, then compare your reasoning. If you keep missing the same distinction, return to the free CCN1 notes before trying another set.

Set up a free CCN1 mock test

Open the CCN1 mock-test setup and choose 5, 10 or all 25 free questions. The optional practice timers are 8, 15 and 38 minutes respectively. Answers receive feedback as you go; submitting gives you a result to review. Questions and Test draw from the same set, so repeating it will include questions you recognise.

These lengths and timers are PlumbRevise revision settings. ACS includes knowledge and practical assessment; your centre confirms its assessment arrangements. A score on this selected set cannot establish readiness for the whole assessment. Premium unlocks the full maintained CCN1 bank, the other gas modules and longer practice sets.

1. Pick a length you can finish and turn the timer on only if you want timed practice.
2. Answer from your own reasoning, then read why the chosen action or calculation works.
3. Submit the set and list the topics behind the mistakes, including answers you guessed correctly.
4. Review those notes and explain the method in your own words before returning to practice.