RGII 5-Year Competency Assessment key terms

UK regulations placing duties on anyone working on gas fittings and appliances, covering competence, safe installation, maintenance, and reporting of unsafe situations in domestic and commercial premises.

The official UK registration body for competent gas engineers. Registration is required by law to work on gas appliances and installations, and the ID card lists the work categories a business is qualified for.

Having the training, qualifications, practical experience and current knowledge needed to carry out a defined gas task safely and to recognised standards, evidenced by certification and registration.

A condition where gas work or an appliance presents a risk of injury, fire, explosion, or carbon monoxide poisoning. It must be classified, made safe, and reported to the responsible person.

Classification for a fault that poses an immediate risk to life or property, such as a major gas leak or unsafe flue. Gas supply must be cut off and the situation reported without delay.

Classification for a defect that is not immediately dangerous but could become so if left, for example poor ventilation or a partially blocked flue. The user must be informed and remedial action agreed.

A documented notice issued to the responsible person when an unsafe situation is found, recording the defect, the action taken, and any appliance or supply isolation applied.

A colourless, odourless fossil fuel supplied mainly as methane with odorant added. It is lighter than air, burns with a blue flame, and has a calorific value around 38-39 MJ/m3.

Propane or butane stored as a liquid under pressure and vaporised for use. It is heavier than air, so leaks collect in low areas such as drains and basements, and it has a higher calorific value than natural gas.

The quantity of heat released when a unit volume or mass of gas is completely burned. Gross value includes latent heat of water vapour; net value excludes it. It determines burner heat input.

A measure of the rate of heat release through a fixed injector, calculated from calorific value divided by the square root of relative density. It indicates whether gases are interchangeable for a given burner.

The ratio of a gas's density to that of air. Values below one mean the gas rises and disperses; values above one mean it sinks and accumulates in low-lying spaces.

The deliberate addition of a pungent sulphur compound to otherwise odourless gas so leaks can be detected by smell at concentrations well below the lower explosive limit.

The minimum concentration of gas in air at which ignition can occur. For methane it is about 5 percent by volume; below this the mixture is too lean to burn.

The maximum concentration of gas in air above which the mixture is too rich to ignite. For methane it is about 15 percent by volume; between LEL and UEL the mixture is flammable.

Burning of a fuel with sufficient oxygen to convert all carbon to carbon dioxide and hydrogen to water vapour, releasing maximum heat and producing a clean blue flame.

Burning with insufficient oxygen or poor mixing, producing carbon monoxide, soot and reduced heat output. It is a serious hazard and indicates a need for servicing or improved air supply.

A colourless, odourless, toxic gas produced by incomplete combustion. It binds to haemoglobin far more readily than oxygen and can cause death in enclosed or poorly ventilated spaces.

A product of complete combustion. Its concentration in flue gases, measured as a ratio with oxygen, indicates combustion quality and excess air levels during flue gas analysis.

Air supplied beyond the theoretical amount needed for complete combustion, expressed as a percentage. Too little causes carbon monoxide; too much wastes heat and cools the flame.

The visual appearance of a burner flame used to judge combustion. A healthy natural gas flame is stable, blue and slightly lifted; yellowing, lifting or sooting indicates a fault.

A smoke test confirming that products of combustion are carried safely away through the flue and that there is adequate draught, with no spillage into the room.

A test using a smoke pellet or detector to check whether combustion products escape from an appliance or flue terminal into the room rather than discharging outdoors.

An electronic instrument that measures oxygen, carbon dioxide, carbon monoxide and temperature in flue gases to calculate combustion efficiency and confirm safe operation.

The supply of fresh air to and removal of stale air from a space. It is required for combustion air, dilution of flue gases and control of condensation and overheating.

Selecting pipe diameter so that gas reaches appliances at adequate pressure and flow rate, accounting for load, pipe length, fittings and permissible pressure drop.

The reduction in gas pressure along a pipe run caused by friction and fittings. It must stay within permitted limits so appliances receive their required working pressure.

The pressure at which gas is delivered to an appliance while it is operating, measured at the test point. It must match the manufacturer's stated value for correct combustion.

The volume of gas consumed by an appliance per unit time, measured at the meter. It is used to check heat input and confirm correct injector sizing and combustion.

The energy supplied to an appliance per unit time, calculated from gas rate and calorific value. It is compared with the manufacturer's rating to verify correct operation.

A pressure test on new or altered gas pipework, using air or gas and a gauge, to prove the installation is leak-free before it is purged and put into use.

The controlled removal of air from new pipework by gas, or of gas by air before work, so that a flammable mixture is not created or left in the system.

A calibrated jet that meters gas into a burner. Its size is matched to the gas type and appliance rating, so fitting the wrong injector alters heat input and combustion.

An unintended release of gas from pipework, fittings or appliances. It must be located, isolated and repaired, with ignition sources removed and the area ventilated.

An instrument that senses flammable gas in air and alarms before the lower explosive limit is reached, used to confirm leaks and check for safe atmosphere.

The process of putting a new or serviced installation into safe operation, including tightness testing, purging, setting pressures, checking gas rates and confirming combustion and safety devices.

Scheduled inspection, cleaning and adjustment of appliances and pipework to keep them safe and efficient, including checking combustion, safety devices, ventilation and flue condition.

A systematic process of gathering symptoms, testing components and interpreting readings to identify the cause of a fault before carrying out a safe repair.