UK trade-and-hazard guidance by the Riskora Editorial Team
Gas Safe registration is the legal baseline for any work on a gas appliance or installation in Great Britain — but registration alone does not satisfy a RAMS reviewer. The tightness test sequence (BS 6891 for natural gas, BS 5482 for LPG), the let-by check, and the strength test where required, all have to be specified in the document. Working in occupied premises adds a CO risk during purging, and the rescue plan for an occupier showing CO symptoms must be written, not improvised.
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Gas Safety (Installation and Use) Regulations 1998
Regulation 3 (qualification of persons)
Only Gas Safe registered persons may work on gas. Registration is mandatory and the work must fall within the scope of the engineer's specific qualifications (CCN1, CENWAT, etc.).
BS 6891 Specification for Installation of Natural Gas Pipework
Section 8 (testing)
Tightness test procedure. Let-by check. Strength test for new installations.
Gas Safe Technical Bulletins
Various (current edition)
Engineer must work to current technical bulletins on tightness testing, CO procedures, and unsafe situation reporting.
Every UK RAMS reviewer applies the hierarchy of controls in the order below. Defaulting straight to PPE is the single most common reason a RAMS fails review.
1. Eliminate
Where a complete change of fuel is contemplated (gas to electric heating), eliminate the gas hazard at source.
2. Substitute
Sleeve gas pipework through any wall penetration to avoid joint exposure to corrosion or accidental damage.
3. Engineering controls
Calibrated pressure gauge (current cert) for tightness test. Continuous CO monitor on engineer and occupier during purging. Mechanical ventilation if work in confined plant room.
4. Administrative controls
Gas Safe ID check by client before start. Tightness test logged on Gas Safe certificate (paper or app). Unsafe situation reporting protocol if an existing fault is found.
5. PPE (last line)
FFP3 RPE for any purging in confined space. Personal CO monitor. Gloves, safety glasses.
Not naming the specific tightness test standard (BS 6891 for natural gas, BS 5482 for LPG) or the test pressure and duration. Reviewers want to see the procedure, not 'tightness test will be carried out'.
An illustrative extract structured for principal-contractor review. Site-specific facts must be substituted and checked by a competent person.
Works carried out by Gas Safe registered engineer (ID 123456, current to 30 Nov 2026, qualifications CCN1, CENWAT, CKR1, HTR1). Existing installation will be isolated at the meter ECV and a let-by check carried out per BS 6891 Clause 8.4. New installation will be strength-tested at 22.5 mbar for 2 minutes, then tightness-tested at 21 mbar for 2 minutes per BS 6891 Clause 8.5. Test medium: air. Calibrated digital manometer (Anton Sprint Pro 2, calibration current to 18 Aug 2026). Personal CO monitor (BW MicroClip XL) worn during all purging activity. Occupier informed in writing before isolation; ventilation increased during purge. Gas Safe certificate raised on completion via Gas Safe app.
Calibration certificate of test equipment checked at sign-on. Personal CO monitor pre-use bump test. Gas Safe ID check by occupier or supervisor. Tightness test results logged on certificate.
Can a non-Gas Safe registered person assist?
An apprentice may assist under the supervision of a Gas Safe registered engineer, but only the registered engineer may work on the gas installation directly and only the registered engineer may issue the certificate.
What test pressure is used for natural gas tightness?
21 mbar test pressure for 2 minutes is the standard tightness test under BS 6891 for new and altered installations on natural gas. Higher strength test pressures (22.5 mbar for new installations) precede the tightness test.
Is a CO monitor mandatory for heating engineers?
Personal CO monitors are not strictly mandatory under regulation but Gas Safe technical bulletins strongly recommend them, and most insurers and principal contractors require them as a condition of access. Working in occupied premises without one is increasingly hard to justify.
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