ie-rgii-non-domestic-gas-safety cheat sheet

Irish gas work is governed by the Gas Safety Act 2012 (as amended) and the Gas Safety (Management) Regulations; RGII is the statutory registration body for gas installers, and unregistered gas work is an offence.

The RGII Criteria Document defines the scope of Registered Gas Installer categories (e.g. domestic natural gas, non-domestic natural gas, LPG) - a non-domestic installer must hold the relevant non-domestic scope before working on commercial or industrial systems.

Non-domestic work must comply with I.S. 820 (non-domestic gas installations) and, for LPG, I.S. 3213 plus the LPG-specific codes; the Standard takes precedence over manufacturer instructions only where the manufacturer is silent or less onerous.

Duties under the Safety, Health and Welfare at Work Act 2005 require risk assessment, competent persons, and safe systems of work; a gas installer is a 'person at work' and also owes duties to non-employees affected by the work.

The Gas Safety (Management) Regulations impose duties on the gas transporter and on persons conveying gas; installations must be safe and gas must not escape. Notifiable incidents (escape, fire, explosion, CO) must be reported to RGII and the gas network operator.

Landlord and owner duties: a 'relevant person' must ensure gas fittings and flueing are maintained in safe condition; non-domestic premises have no statutory periodic inspection like domestic, but insurance and licensing often require documented inspection.

Building Regulations Part J (heat producing appliances) and Part L (conservation of fuel and energy) apply to non-domestic installations; a completion certificate or Declaration of Conformity may be required where works are notifiable.

Records must be retained: installation, commissioning, tightness test, and warning notice copies. RGII requires the installer to leave a warning notice (and notify RGII) where an immediate danger is found and the supply is isolated.

Working on a gas installation without the owner's authority, or reconnecting an isolated supply without remedying the defect, is prohibited; only the person who isolated (or a competent successor) may restore supply after corrective action.

Natural gas (predominantly methane) calorific value is about 38–39 MJ/m³ gross; LPG (propane/butane mix) is about 93–95 MJ/m³ (propane) and 120–125 MJ/m³ (butane) gross per m³ of vapour - so LPG requires much smaller pipe sizes for the same heat input.

Relative density: natural gas ~0.6 (lighter than air, rises and vents at high level); LPG vapour ~1.5–2.0 (heavier than air, accumulates at low level, in ducts, pits, basements and drains). This drives ventilation and detector placement.

Stoichiometric air requirement: methane needs ~9.5 m³ air per m³ gas (≈2 volumes O₂); propane needs ~23.8 m³ air per m³ vapour. Wobbe index and aeration settings must match the gas family declared on the appliance data plate.

Flammable limits: methane ~5–15% by volume in air; propane ~2.1–9.5%; butane ~1.8–8.4%. LPG therefore has a wider and lower explosive range, increasing risk in confined spaces.

Complete combustion produces CO₂ and water; incomplete combustion produces CO, which is toxic (TWA 8-hour limit ~30 ppm, STEL ~200 ppm under Irish OELs). CO is colourless, odourless and slightly lighter than air, so it mixes readily.

LPG is stored as liquid under pressure; 1 litre of liquid propane yields ~0.27 m³ of vapour at 15 °C, and vapour pressure rises with temperature (propane ~7.5 bar at 20 °C). Vessels and pipework must be rated for the maximum vapour pressure at the site's design temperature.

Commercial/industrial burners often use forced draught and premix; flame speed and burner port loading govern light-back and flame-lift risk. Natural gas has lower flame speed than LPG, so injector sizing and aeration differ between families.

Gas/air explosions in confined plant rooms need confinement and ignition; gas detection, ventilation and emergency isolation are the primary controls. Odorisation (mercaptan/THT) allows smell detection at ~1/5 of the lower flammable limit, but odour fade can occur in new steel pipe and in LPG.

Pipe sizing uses the gas rate (m³/h) and an allowable pressure drop; for low-pressure natural gas, typical design pressure drop is 1 mbar (or as specified) from meter outlet to appliance, using tables/graphs for the chosen material and gas family.

Equivalent length method: add the measured length to equivalent lengths for each fitting (elbow, tee, valve) from the manufacturer's or standard's table, then size against the total equivalent length and heat input.

Materials: for natural gas, steel (threaded or welded), copper (with appropriate jointing), and PE for buried service; LPG requires materials compatible with the liquid/vapour and suitable for higher pressures, with no copper downstream where the gas may contain aggressive compounds.

Joints: threaded joints use approved sealing compound or PTFE tape compatible with the gas; compression fittings must be rated for gas; flanged joints use suitable gaskets. Soldered copper joints must use lead-free solder and appropriate flux, fully cleaned.

Pipework must be supported at intervals appropriate to material and diameter, protected against corrosion, isolated from electrical earth bonding requirements (main equipotential bonding at the meter), and sleeved where passing through walls.

Ventilation of voids, ducts and shafts containing gas pipework is required where gas could accumulate; LPG pipework must not pass through unventilated voids where leakage could collect, and must be routed to prevent liquid trapping.

Isolation: an accessible isolation valve must be provided at the meter/regulator outlet and at each appliance or zone; emergency control valves must be clearly marked and accessible, and for LPG the vessel outlet valve is the primary emergency control.

Pressure regimes: low pressure (typically <75 mbar), medium pressure (75 mbar to 2 bar) and high pressure (>2 bar) have different design, testing and jointing rules; non-domestic installations frequently use medium-pressure supplies with a site regulator.

Pipework must be labelled with gas type and flow direction where multiple gases or routes exist; buried pipework requires marker tape and recorded route drawings handed to the client.

Appliance data plates declare gas family, nominal heat input, gas rate, burner pressure, injector size and flue type; commissioning must match the declared values and the appliance must be suitable for the installation's gas family and supply pressure.

Flue types: Type B (open flue, room air), Type C (room-sealed, balanced flue), and Type A (no flue, e.g. some industrial burners); non-domestic appliances commonly use forced-draught burners with flue dilution or mechanical extract.

Flue design must maintain the manufacturer's required draught and terminal positions relative to openings, windows, boundaries and other flues; flue dilution factors and extract rates must be calculated, not assumed.

Controls: flame supervision (flame rectification or UV/IR detection), automatic ignition, overheat and limit thermostats, gas pressure switches, air pressure switches on forced-draught burners, and safety shut-off valves (SSOVs) that close on flame failure.

Burner management systems (BMS) for industrial burners must provide pre-purge, proved ignition, flame proving and post-purge; safety shut-off valves must be proved closed before light-up and on shutdown, with leak test where required.

Gas pressure regulators (service and appliance) must be vented safely; regulator vents must not discharge where gas can accumulate, and LPG regulator vents must be routed outdoors away from openings.

Flueing materials must be rated for the flue gas temperature and condensate conditions; condensing appliances need condensate drainage with trap and neutralisation where required, and flue terminals must resist wind and recirculation.

Air for combustion must not be drawn from a contaminated atmosphere (e.g. near solvents, refrigerants or dust); plant rooms with forced-draught burners require interlocked ventilation proving before firing.

Ventilation serves three purposes: combustion air, dilution of flue gases (for open-flue appliances), and cooling of plant/control rooms; each must be calculated separately and the largest requirement governs.

For open-flue appliances, combustion air is typically sized from the appliance input (e.g. a free area per kW of input); dilution air is sized separately, and both must be permanent, unobstructed openings sized for the appliance's declared input.

Room-sealed (Type C) appliances take combustion air directly from outside via the balanced flue, so combustion air openings may not be required, but ventilation for cooling and for any other appliances in the space still applies.

Plant rooms with forced-draught burners require low-level and high-level ventilation openings; low-level supplies combustion air, high-level vents dilution/heat. Openings must be non-closable, protected with grilles, and their free area stated after allowing for louvre blockage.

LPG is heavier than air: ventilation must include low-level openings and, for below-ground or basement plant rooms, mechanical extract at low level with interlock to the gas detection and firing controls.

Mechanical ventilation must be interlocked so burners cannot fire unless airflow is proved; a proven air pressure switch or airflow sensor is required, and failure must shut down the burner safely.

Ventilation openings must not be obstructed by storage, and their location must avoid recirculation of flue products or contaminated air into the combustion air supply; terminals and openings must be separated by the manufacturer's/standard's minimum distances.

Documenting ventilation: record opening sizes, free areas, mechanical extract rates and interlock test results in the commissioning record; alterations to the building envelope or openings invalidate the original calculation.

Flue gas analysis measures O₂, CO, CO₂, flue temperature and ambient temperature; from these, calculate CO₂ (or use O₂ to derive excess air), CO/CO₂ ratio, and efficiency.

CO/CO₂ ratio is the key indicator of incomplete combustion: values around 0.004 or below are normal for natural gas; rising ratios (e.g. >0.008) indicate poor combustion and must be investigated.

Excess air: O₂ readings of ~3–6% (natural gas) are typical for correct combustion; very low O₂ risks CO, very high O₂ wastes heat. CO₂ should approximate the appliance's declared value at correct aeration.

Flue draught must be measured with the appliance running and all other appliances in the space operating; a spillage test confirms open-flue appliances clear products under worst-case conditions (doors/windows closed, extract fans running).

CO safety: a CO alarm is not a substitute for combustion analysis; ambient CO in the room must be checked where combustion products may escape, and any CO reading in the breathing zone above background requires investigation and likely isolation.

Test conditions: stabilise the appliance at full rate, use calibrated analysers with in-date calibration, sample at the correct point (manufacturer's test point or flue), and record all readings with ambient conditions.

Efficiency calculation from flue loss: gross/net efficiency derived from flue temperature and CO₂/O₂; condensing appliances show lower flue temperatures and recover latent heat, so efficiency >90% (net) is expected.

Where combustion cannot be proven safe (high CO/CO₂, spillage, inadequate draught), isolate the appliance, attach a warning notice, inform the responsible person and record the action; do not leave the appliance operating.

Tightness testing must use a suitable test medium (air or inert gas - never oxygen or flammable gas for strength testing) and a calibrated gauge/manometer; the test pressure and duration depend on the operating pressure and the standard's tables (e.g. I.S. 820 / IGE/UP/1 procedures).

For low-pressure installations, a common approach is to test at a defined pressure above operating (e.g. 1.5× operating, minimum 20 mbar) for a stabilisation period then a test period, with allowable pressure drop calculated from the installation volume.

Medium- and high-pressure systems require strength testing at higher pressure followed by a tightness test; test pressures and durations must follow the applicable standard and the pipework's design pressure, with gauges of suitable range and accuracy.

Purging: new or reopened pipework must be purged of air before gas is introduced and purged of gas before being opened to atmosphere; purge volumes are calculated from pipe volume and the acceptable gas concentration, with discharge to a safe location.

Purging must not discharge into confined spaces; LPG purging requires particular care due to its density, and ignition sources must be controlled during purge and commissioning.

Commissioning sequence: confirm tightness, purge, set regulator/burner pressures to data-plate values, check gas rate, perform combustion analysis, confirm ventilation and flueing, test safety controls (flame failure, limit stats, interlocks) and record results.

Decommissioning: isolate and lock off the supply, purge gas from the section, disconnect and cap/plug pipework, remove or make safe appliances, label the installation as decommissioned, and update records and the client.

Warning notices: where an installation is unsafe, attach a warning notice, isolate the affected section, inform the responsible person in writing, and notify RGII where required; the notice must state the defect and the action taken.

Fixed gas detection is required where gas can accumulate (plant rooms, basements, LPG stores, boiler houses) and for toxic CO risk; detectors must be selected for the gas, range and environment, and calibrated per manufacturer intervals.

Placement: natural gas detectors at high level near potential leak points and the ceiling; LPG detectors at low level (typically 150–300 mm above floor) because vapour is heavier than air; CO detectors at breathing height in occupied/plant areas.

Detection systems should alarm at two stages (e.g. pre-alarm ~10% LFL and alarm ~20% LFL for flammable gas), with the alarm stage isolating the gas supply and shutting down burners, and activating ventilation and audible/visual alarms.

Emergency procedures: on gas escape - eliminate ignition sources, do not operate electrical switches, isolate the gas at the emergency control valve, ventilate, evacuate and call the gas network emergency service (for natural gas, 1850 20 50 50 in Ireland) and emergency services.

Emergency control valves must be clearly marked, accessible and known to site staff; LPG vessel emergency valves and bulk tank isolation must be included in the emergency plan and drills.

Safety management: permit-to-work systems for hot work and confined spaces, isolation/lock-off procedures, competent persons, and documented emergency drills; gas work in occupied commercial premises requires coordination with the responsible person.

CO alarm response: treat as a gas/CO emergency - ventilate, evacuate, isolate appliances, do not re-enter until declared safe, and have the installation inspected by a competent person before reuse.

Incident reporting: record escapes, fires, explosions and CO incidents; report notifiable incidents to RGII and the relevant authorities, and preserve evidence for investigation.

The commissioning record/handover pack must include: installation details, gas family and supply pressure, pipework sizes and routes, tightness test results, purge records, appliance data-plate values, burner pressures, gas rates, combustion analysis results, ventilation details and flueing details.

Certification: a Declaration of Conformity/completion certificate is issued for notifiable works; RGII registration number and installer details must appear, and the certificate must identify the scope of work and any limitations.

Warning notices and defect records must be copied to the responsible person and retained; where an installation is left isolated, the record must state who isolated it and what is required before reconnection.

As-built drawings and schematics should be updated for pipework changes, including isolation valve locations, detector positions and emergency controls; the client must receive them at handover.

Maintenance and inspection records: non-domestic installations should have a documented inspection/maintenance regime; records of previous tests inform the current inspection and must be reviewed before work starts.

Handover must include demonstration and instruction to the responsible person on emergency controls, isolation points, detector alarms and what to do on gas escape; record who received the instruction.

Records retention: keep copies of test certificates, combustion readings and warning notices for the period required by the standard/insurer (commonly at least the interval to the next inspection); electronic copies are acceptable if retrievable.

Gas detector and analyser calibration certificates should be retained with the installation records to demonstrate that test instruments were in calibration at the time of testing.