Gas Safe Registration (ACS) Core Gas Safety (CCN1) - Domestic Natural Gas Foundation Syllabus

Core Gas Safety (CCN1) - Domestic Natural Gas Foundation syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Core Gas Safety (CCN1) - Domestic Natural Gas Foundation in Gas Safe Registration (ACS), not a summary of it.

1. 1

   Gas Properties, Combustion and Industry Context

   4 topics

   • Composition and characteristics of natural gas
     • Methane content, odorant (mercaptan) and detection by smell
     • Relative density, flammability limits (LFL/UFL) and ignition temperature
     • Calorific value, Wobbe number and stoichiometric air requirement
   • Principles of complete and incomplete combustion
     • Combustion equation and the air-to-gas ratio
     • Products of complete combustion: CO2 and water vapour
     • Causes and indicators of incomplete combustion and CO production
   • Flame characteristics and burner types
     • Aerated vs non-aerated (post-aerated) burners
     • Flame lift, light-back and yellow tipping
   • Structure of the gas industry and the supply chain
     • Transporter, supplier and Gas Safe registered installer roles
     • Emergency Service Provider (gas escape) responsibilities
2. 2

   Legislation, Standards and Documentation

   5 topics

   • Gas Safety (Installation and Use) Regulations 1998
     • Duties of the engineer, employer, landlord and user
     • Definition of competence and the requirement to be registered
     • Action on encountering Immediately Dangerous and At Risk situations
   • Supporting legislation and codes of practice
     • Health and Safety at Work etc. Act 1974
     • Building Regulations Part J / equivalent devolved standards
     • RIDDOR reporting of dangerous gas fittings
   • British Standards and IGEM Technical Standards
     • BS 6891 installation pipework
     • IGEM/UP/1B tightness testing and purging procedures
     • Manufacturer instructions taking precedence
   • The Gas Safe Register and Notification
     • Registration, ID card and scope of categories held
     • Building Regulations notification of installed appliances
   • Records and certification
     • Landlord Gas Safety Record (CP12) requirements
     • Warning/advice notices and labelling defective appliances
3. 3

   Gas Installation Pipework and Tightness Testing

   4 topics

   • Pipe sizing and material selection
     • Calculating discharge using gas rate and permissible pressure drop
     • Copper, steel and corrugated stainless steel tube selection
     • 1 mbar maximum pressure drop allowance across installation
   • Pipework installation requirements
     • Protection against corrosion and mechanical damage
     • Pipes in voids, sleeving through walls and equipotential bonding
     • Routing relative to other services and fire-stopping
   • Let-by and tightness testing procedure (IGEM/UP/1B)
     • Stabilisation period and let-by test
     • Permissible pressure drop for installation volume and meter type
     • Action on a failed tightness test and tracing leaks
   • Purging procedures
     • Direct purging of small installations
     • Safe disposal of purged gas and avoidance of ignition sources
4. 4

   Meters, Controls and Pressure/Gas Rate

   4 topics

   • Gas meters and emergency control valve
     • Meter types, location and protection requirements
     • Emergency Control Valve identification and operation
     • Position of the meter regulator and lock-up pressure
   • Working pressure and standing pressure measurement
     • Using a manometer at the appliance test point
     • Acceptable inlet operating pressure of 21 mbar nominal
   • Gas rating an appliance
     • Timed meter dial / metric meter calculation method
     • Converting measured rate to heat input in kW
     • Comparing measured input against data plate
   • Service and control valves
     • Identification of isolation valves
     • Test point connections and capping unused outlets
5. 5

   Ventilation, Flues and Combustion Performance

   4 topics

   • Ventilation requirements for gas appliances
     • Open-flued vs room-sealed ventilation needs
     • Calculating free air vent area per kW (BS 5440-2)
     • Compartment and high/low ventilation requirements
   • Flue types and classification
     • Open flue, room-sealed (balanced) and fanned flues
     • Flue terminal positioning and clearances (BS 5440-1)
   • Flue flow and spillage testing
     • Flue flow test using smoke pellet/match
     • Spillage test method and acceptance criteria
   • Combustion analysis
     • Using a flue gas analyser and CO/CO2 ratio
     • Maximum acceptable CO/CO2 ratio of 0.004
6. 6

   Emergency Procedures, CO Awareness and Unsafe Situations

   4 topics

   • Gas escape and emergency response
     • Actions on smelling gas and using the National Gas Emergency number
     • Ventilation, ignition source control and evacuation
   • Carbon monoxide hazards
     • Physiological effects and symptoms of CO poisoning
     • CO alarms to BS EN 50291 and siting
   • Gas Industry Unsafe Situations Procedure
     • Classifying Immediately Dangerous (ID) installations
     • Classifying At Risk (AR) installations
     • Riddor reporting and turning off/disconnecting with consent
   • Warning labels and customer communication
     • Affixing danger/warning notices
     • Obtaining signed permission to disconnect

Core Gas Safety (CCN1) - Domestic Natural Gas Foundation flashcards for Gas Safe Registration (ACS)

24 of 51 cards from the Core Gas Safety (CCN1) - Domestic Natural Gas Foundation deck — real questions with worked answers.

1. What is the approximate volumetric composition of UK natural gas, and which compound is the dominant constituent?

   UK natural gas is predominantly methane ($\ce{CH4}$) at roughly $90\text{–}95\%$, with smaller amounts of ethane ($\ce{C2H6}$), propane, butane, nitrogen and carbon dioxide. Methane is the dominant constituent.

2. List the key physical characteristics of natural gas: relative density, odour, flammability limits and ignition temperature.

   Relative density approximately $0.6$ (lighter than air, which is $1.0$); naturally odourless (odorant/stenching agent added); flammable in air between roughly $5\%$ and $15\%$ gas-in-air; ignition (auto-ignition) temperature about $650\,^{\circ}\text{C}$.

3. What is the calorific value (CV) of UK natural gas and what does it represent?

   Approximately $38.7\ \text{MJ/m}^{3}$ (around $1040\ \text{Btu/ft}^{3}$). The calorific value is the amount of heat energy released when a unit volume of gas is completely burned.

4. What is the chemical equation for the complete combustion of methane?

   $$\ce{CH4 + 2O2 -> CO2 + 2H2O}$$ Methane reacts with oxygen to give carbon dioxide and water vapour, releasing heat.

5. What are the products and the visible flame colour of complete combustion of natural gas?

   Products are carbon dioxide ($\ce{CO2}$) and water vapour ($\ce{H2O}$), with heat. The flame is clear blue and stable, indicating sufficient air supply.

6. What is incomplete combustion, what dangerous product does it form, and what causes it?

   Combustion with insufficient oxygen, producing carbon monoxide ($\ce{CO}$), carbon and water, e.g. $\ce{2CH4 + 3O2 -> 2CO + 4H2O}$. Caused by lack of air/ventilation, blocked flue, incorrect gas/air mix or sooted-up burner. The flame is yellow/sooty.

7. What three conditions are required for combustion (the combustion triangle)?

   Fuel (gas), oxygen (air) and an ignition source (heat). Removing any one of the three stops or prevents combustion.

8. Compare a pre-aerated (aerated) burner with a post-aerated (non-aerated) burner.

   Pre-aerated burner: gas mixes with primary air before the burner port, giving a hot, clear blue flame (e.g. Bunsen-type). Post-aerated burner: gas burns drawing all air at the flame, giving a softer luminous flame; air is supplied only as secondary air.

9. Define primary air and secondary air in relation to a gas flame.

   Primary air is air drawn into and mixed with the gas before it reaches the burner port. Secondary air is air supplied to the flame at the point of combustion to complete the burning of the gas.

10. What are flame lift and light-back (flashback / striking-back) and what causes each?

    Flame lift: the flame lifts off the burner ports because gas velocity is too high (often excess pressure/primary air). Light-back: the flame burns back inside the burner because gas velocity is too low or ports are too large, causing burning at the injector.

11. Outline the structure of the UK gas supply chain from source to consumer.

    Production/import (offshore fields, LNG terminals, interconnectors) → National Transmission System (high-pressure transmission, operated by National Gas Transmission) → local Distribution Networks (GDNs, reducing pressure) → service pipe → consumer's emergency control valve and meter.

12. What is the role of a Gas Distribution Network (GDN) and what is the emergency number for reporting a gas escape?

    A GDN owns and operates the local lower-pressure pipes that deliver gas from the transmission system to consumers' premises and maintains the network. The National Gas Emergency Service number is $0800\ 111\ 999$.

13. What is the title and purpose of GSIUR 1998?

    The Gas Safety (Installation and Use) Regulations 1998 — the principal statutory law governing the safe installation, maintenance and use of gas fittings, appliances and flues in domestic and commercial premises, made under the Health and Safety at Work etc. Act 1974.

14. Under GSIUR 1998, who is legally permitted to carry out work on gas fittings?

    Only a competent person who is a member of a class of persons approved by the HSE — in practice, an operative employed by a business registered with the Gas Safe Register and holding current ACS competence for the work.

15. Under GSIUR Regulation 26(9), what must be checked when work is done on a gas appliance? (the four safety checks)

    1) Effectiveness of any flue; 2) Supply of combustion air; 3) Operating pressure or heat input (or both); 4) Operation of the appliance to ensure safe functioning. These constitute the appliance safety check.

16. Name the key supporting legislation that underpins gas work in the UK.

    Health and Safety at Work etc. Act 1974 (HSWA), Management of Health and Safety at Work Regulations 1999, Gas Safety (Management) Regulations 1996 (GSMR), Pipelines Safety Regulations 1996, COSHH 2002, and the Construction (Design and Management) Regulations.

17. What does an Approved Code of Practice (ACOP) provide, and what is its legal status?

    An ACOP gives practical guidance on how to comply with the law (e.g. L56 for GSIUR). It has special legal status: if you are prosecuted and did not follow it, you must show you complied with the law in another way, or a court may find you at fault.

18. What do British Standards and IGEM Technical Standards provide, and are they law?

    They are recognised technical specifications defining good practice for materials, installation, testing and safety. They are not law themselves but are the accepted way to demonstrate compliance with GSIUR; deviation must be justified as equally safe.

19. What does IGEM stand for and what type of documents does it publish?

    The Institution of Gas Engineers and Managers. It publishes technical standards (e.g. IGEM/UP, IGEM/G series) covering pipework, tightness testing, purging and installation procedures for gas systems.

20. Which IGEM standard governs domestic tightness testing and purging, and which covers domestic pipework sizing/installation?

    IGEM/UP/1B covers tightness testing and direct purging for low-pressure domestic installations. IGEM/G/5 (and BS 6891) covers domestic natural gas pipework installation and sizing for pipes up to $35\ \text{mm}$.

21. What is the Gas Safe Register and what does it replace?

    The Gas Safe Register is the official statutory body for gas registration in Great Britain, Isle of Man and Guernsey. It replaced CORGI in April 2009 as the registration scheme that legally must be held by anyone working on gas.

22. What is a Building Regulations notification and who notifies for registered gas engineers?

    Notifiable work (e.g. installing a boiler or fire) must be notified to Building Control. Gas Safe Register operates a self-certification scheme: the registered installer notifies Gas Safe Register, who informs the local authority and issues a Building Regulations Compliance Certificate to the customer.

23. What is a Gas Safety Record (Landlord/CP12) and how often is it required?

    A record of the safety check carried out on each gas appliance and flue in rented property. Landlords must have an annual gas safety check (every 12 months) by a registered engineer and provide the record to tenants.

24. What is a Benchmark commissioning checklist used for?

    Benchmark is the industry standard installation, commissioning and service record (logbook) for domestic heating appliances; completing it validates the manufacturer's warranty and records that the appliance was installed and commissioned correctly.

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