CCN1 Study Guide 2026
Everything you need to pass the CCN1 exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 CCN1 Exam Format at a Glance
📚 CCN1 Topics to Study (27)
✍️ Sample CCN1 Questions & Answers
1. What component must be fitted where a gas flue pipe passes through a combustible material such as a timber floor or wall?
Where a gas flue pipe passes through combustible material (such as a timber floor, ceiling, or wall), a non-combustible fire-resistant sleeve must be fitted. There must be a minimum 25 mm air gap between the flue pipe and the combustible material, filled with non-combustible material if necessary. This prevents heat transfer from the flue igniting the surrounding structure.
2. Under the Health and Safety at Work etc. Act 1974, what is the primary duty placed upon employers regarding gas work?
Section 2 of the Health and Safety at Work etc. Act 1974 places a general duty on employers to ensure, so far as is reasonably practicable, the health, safety, and welfare at work of all employees. Section 3 extends this duty to non-employees who may be affected by the undertaking.
3. What is the purpose of a CO alarm in a domestic property?
CO alarms provide an audible warning when CO concentrations rise, giving occupants time to evacuate before reaching dangerous levels. They are the only way to detect CO, which has no smell or colour.
4. What is 'vitiation' in the context of gas appliance operation?
Vitiation occurs when an open-flued or flueless appliance consumes oxygen from the room for combustion, progressively reducing the oxygen level in the space. This can lead to incomplete combustion, increased carbon monoxide production, and ultimately a dangerous situation if adequate ventilation is not provided.
5. What is the standard working pressure for natural gas supplied to domestic properties in the UK?
The standard working pressure for natural gas in UK domestic properties is 21 mbar (approximately 8.4 inches water gauge). This is the nominal pressure maintained by the gas distribution network at the meter outlet. Engineers must verify this pressure when commissioning or servicing appliances.
6. What is the maximum permissible pressure drop on a let-by test of a gas meter?
A let-by test checks whether the meter's internal valve (ECV closed, downstream open) is passing gas. The test is performed with the ECV closed and the pressure monitored. Any rise in pressure on the installation side indicates the ECV is letting by, which constitutes a gas escape that must be reported to the gas transporter.