Gas Safety Defect Categories Explained: ID, At Risk, and NCS for Landlords

The Three Classifications

When a Gas Safe engineer finds a problem during your annual check, they classify the defect under the Gas Industry Unsafe Situations Procedure (IGEM/G/11). Three categories exist, and each triggers a different level of urgency:

Immediately Dangerous (ID): The appliance or installation poses a direct, present danger to life or property. Think cracked heat exchangers leaking carbon monoxide, blocked flues with combustion products spilling into the room, or gas leaks from corroded pipework.

At Risk (AR): The appliance has a defect that could become dangerous if left uncorrected. The hazard isn't immediate, but it's real and deteriorating. Examples include partially blocked flues, intermittent safety devices, or ventilation that's inadequate for the appliance rating.

Not to Current Standards (NCS): The appliance or installation was fitted to the standards of its era but doesn't comply with today's installation requirements. It isn't currently dangerous and isn't expected to become dangerous in normal use. An older boiler with an adequate flue but no condensate drain, for instance.

What Happens at Each Level

Immediately Dangerous: The engineer must disconnect the gas supply to the appliance with the occupant's consent and attach a red Danger Label (or "Danger — Do Not Use" notice). The appliance stays off until a qualified engineer repairs the fault, re-tests, and issues a passing safety record. If the tenant or landlord refuses to let the engineer disconnect, they are obligated under Regulation 34 to notify the gas transporter (the network operator), who has the power to turn off the external gas supply to the entire premises.

At Risk: The engineer turns off the appliance with the occupant's consent and attaches a yellow Warning Label. The appliance cannot be used until repairs are completed and a fresh check confirms it's safe. The timeline is less urgent than ID, but "less urgent" doesn't mean optional — the appliance is off-limits until it passes.

Not to Current Standards: The engineer records the finding on the Landlord Gas Safety Record and advises the landlord on recommended upgrade paths. There is no requirement to take immediate remedial action, but the note stays on the record. Future inspections will flag it again, and it becomes a maintenance planning item.

Your Obligations as the Landlord

For ID and AR findings, the action sequence is the same:

1. Arrange repairs immediately. Engage a Gas Safe registered engineer — the same engineer who found the defect can often do the repair, or they may recommend a specialist.
2. Get a fresh passing record. Once repairs are complete, the engineer re-tests and issues a new Landlord Gas Safety Record confirming all items pass. The old record with the defect notation stays in your file; the new one replaces it as the current compliance document.
3. Serve the updated record. Deliver the new record to existing tenants within 28 days. If a new tenant is due to move in, they need the passing record before occupation.
4. Keep the repair evidence. File the contractor's invoice specifying what was replaced or repaired, alongside the fresh record. Financial proof alone (a bank transfer, a quote) doesn't satisfy the statutory requirement — you need the signed, passing safety record.

For NCS findings, no immediate repair is legally required. But be aware that NCS items can deteriorate over time into AR or ID situations. If the engineer recommends an upgrade — replacing an old boiler, improving ventilation — treat it as a maintenance investment, not a compliance nuisance.

Temporary Measures During Repairs

If a boiler is disconnected as Immediately Dangerous during winter, your tenants still need heating. You're responsible for providing temporary alternatives: electric radiators, fan heaters, or portable oil-filled heaters. This isn't a statutory requirement under GSIUR specifically, but the property must remain habitable under the Housing Act 2004 and the Landlord and Tenant Act 1985 (Section 11 implied repair obligations).

For gas hobs or ovens disconnected as ID or AR, provide a temporary electric cooking appliance if possible, or direct tenants to alternative arrangements.

What a Defect Means for Your Compliance Status

A defect on your CP12 doesn't mean your annual check obligation was unmet — the check happened, the defect was found, and that's the system working correctly. Your compliance status depends on what you do next. An ID finding with same-week repairs, a fresh passing record, and evidence of the whole sequence is a landlord doing their job. An ID finding followed by months of inaction is an enforcement target.

Our Gas Safety Compliance Guide includes a defect remediation tracker — a log sheet that ties the original defect, the repair contractor, the repair date, and the fresh passing record into a single audit-ready document.

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