RGII Domestic Gas Safety flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Gas Safety (Installation and Use) Regulations

UK regulations governing the safe installation, maintenance and use of gas fittings and appliances in domestic and commercial premises, placing duties on installers, landlords and users.

Landlord gas safety check interval

A landlord must have every relevant gas appliance and flue checked for safety at intervals of no more than 12 months and give the record to tenants within 28 days.

Regulation 36 bathroom restriction

No gas appliance may be installed in a room used as a bathroom or shower room unless it is a room-sealed appliance, protecting occupants from combustion products and gas escape.

BS 6891 scope

British Standard covering the installation of low-pressure gas pipework of up to 35 mm nominal size in domestic and similar premises, including testing and purging requirements.

Relative density of natural gas

Natural gas is about 0.6 times as dense as air, so it rises and disperses at high level; this affects where leaks accumulate and how ventilation is designed.

Relative density of LPG

Propane has a relative density of roughly 1.5-2.0, so it is heavier than air and collects in low-lying areas such as basements, pits and drains.

Complete combustion equation for methane

CH4 + 2O2 produces CO2 + 2H2O; each volume of methane needs about two volumes of oxygen, roughly ten volumes of air.

CO/CO2 ratio threshold

A flue gas analyser ratio above 0.004 indicates incomplete combustion and a potentially unsafe appliance, requiring investigation and possible isolation.

Flammable limits of natural gas

Natural gas is flammable in air between approximately 5% and 15% by volume; below or above this range the mixture will not ignite.

Pipework sleeving requirement

Where gas pipe passes through a wall, floor or cavity, a sleeve must be fitted and sealed to the structure, with the annular space left open so leaking gas can disperse.

Let-by test purpose

A let-by test checks that the meter valve or test nipple is not passing gas before a tightness test, preventing a false result from a leaking internal valve.

Tightness test medium

Tightness tests use air or inert gas, never gas; test pressure and permissible drop are taken from BS 6891 tables based on installation volume and duration.

Purging new pipework

Purging displaces air from new or altered pipework with gas before lighting; the volume is calculated from pipe internal volume and the required number of volume changes.

Emergency control valve location

The ECV is fitted at the point where the service pipe enters the premises or on the meter outlet, must be readily accessible and operable without tools.

Meter regulator outlet pressure

For natural gas, the meter regulator outlet pressure should typically be within about 19-23 mbar; the operating pressure at the appliance is checked at its test point.

Main protective bonding position

Main protective bonding of metallic gas pipework must be within 600 mm of the meter outlet on the consumer side, in accordance with the IET Wiring Regulations.

Gas escape at meter procedure

If a leak is suspected at the meter or service, turn off the ECV, ventilate the area, avoid flames and electrical switches, and notify the gas transporter.

Gas rate check calculation

The gas rate is measured from the meter dial over a timed period and converted to kW using the calorific value of the gas and the meter conversion factor.

Commissioning operating pressure check

The burner operating pressure is measured at the appliance test point and compared with the data plate value; it must fall within the manufacturer's tolerance.

Room-sealed appliance definition

A room-sealed appliance takes combustion air directly from outside and discharges products outside, so it does not draw air from the room it serves.

Servicing heat exchanger inspection

Servicing includes inspecting the heat exchanger, burner, seals and flue for damage or blockage, cleaning as needed and confirming combustion performance with an analyser.

Flue terminal distance from opening

BS 5440 Part 1 specifies minimum terminal distances, including about 300 mm from an opening window or door and 600 mm from a boundary or neighbouring building.

Draught diverter function

A draught diverter on an open-flued appliance prevents down-draught affecting combustion and allows combustion products to spill into the room if the flue becomes blocked.

Flue flow test method

A smoke pellet is burned in the appliance flue to confirm the flue draws correctly and that smoke is discharged at the terminal, not into the room.

Spillage test procedure

A flame or smoke is held at the draught diverter after the appliance has run; products must be drawn into the flue, with no spillage into the room.

Flue terminal guard requirement

A terminal guard must be fitted where the flue terminal is accessible to the public or could be touched, to prevent contact with hot or sharp components.

Immediately Dangerous classification

An ID situation poses an immediate risk to life or property; gas must be shut off, the appliance isolated, a warning notice issued and the customer informed not to use it.

At Risk classification

An AR situation is a fault that could become dangerous; the appliance should be isolated, a warning notice issued and the customer advised of the defect and required action.

Warning notice contents

A warning notice records the defect, date, engineer details and action taken; the customer should sign to acknowledge receipt and a copy is retained.

Carbon monoxide alarm guidance

CO alarms should be fitted in rooms with open-flued appliances and in sleeping areas where guidance requires; an alarm does not replace correct servicing and checks.

Reconnection after ID classification

An appliance classified ID may only be reconnected once the defect has been rectified, the appliance retested and found safe, and the customer informed.

Combustion analysis record

Combustion analysis records CO, CO2, O2 and the CO/CO2 ratio; results are compared with manufacturer limits and retained as part of the commissioning or service record.