Gas unsafe situations procedure: ID, AR and NCS explained

Where the rules come from: GSIUR and GIUSP

Two things are easy to mix up. The Gas Safety (Installation and Use) Regulations 1998 — GSIUR — are the law. They set the duties: only competent, Gas Safe registered people work on gas, and anyone who knows of a gas fitting that is or may be dangerous has to act on it rather than leave it. GSIUR says you must deal with an unsafe situation; it does not spell out the step-by-step method.

The method is the Gas Industry Unsafe Situations Procedure — GIUSP — published in IGEM/G/11 and summarised for engineers in Gas Safe Technical Bulletin 001 (TB 001). GIUSP is what turns "this is unsafe" into a defined classification and action. So in revision terms: GSIUR is the legal duty, GIUSP is how you carry it out. If a question asks what you must do about a defect, it is testing GIUSP; if it asks who may work on gas or what the law requires, it is testing GSIUR.

This page is revision support, not authority to carry out gas work. Live testing, disconnection and making safe are for competent Gas Safe registered engineers following the current procedure and manufacturer instructions.

The unsafe categories and the separate NCS description

GIUSP uses two unsafe classifications: ID and AR. NCS was removed from the procedure because it describes a safe standards shortfall. Businesses may still record and advise on that shortfall separately.

• Immediately Dangerous (ID): a danger to life or property is present now, or would be the moment the appliance or installation is used. This is the most urgent outcome.
• At Risk (AR): one or more recognised faults exist that are not a danger right now but could become one in use. Serious, but not an immediate emergency.
• Not to Current Standards (NCS): a safe standards shortfall, outside the current GIUSP unsafe classifications. Record and advise separately.

The two questions that sort any defect

You do not memorise a list of which faults are ID and which are AR — installations differ, and the assessment rewards the reasoning, not rote recall. Instead you ask two questions in order.

• Question one: is this a danger to life or property now, or would it be as soon as the appliance is used? If yes, it is Immediately Dangerous and you stop there.
• Question two (only if the first is no): could this defect become a danger to life or property in use? If yes, it is At Risk.
• Where assessment establishes a safe standards shortfall, record and explain it separately. NCS is not a third GIUSP unsafe category.

Immediately Dangerous (ID): the action

For an ID situation the priority is to remove the danger. With the customer’s permission, turn off and disconnect the appliance or installation and make it safe, attach an Immediately Dangerous warning label, and issue a warning notice recording what you found and did. The point examiners look for is that you leave the situation safe, not merely documented.

Permission is the twist. You cannot force your way onto a customer’s appliance — turning off and disconnecting needs their agreement. If permission to make safe is refused, you must warn the responsible person clearly of the danger, and, because an ID situation can involve escaping gas or an immediate risk to people, contact the gas emergency service. The National Gas Emergency number is 0800 111 999. A "safe" answer never involves leaving a known immediate danger connected and simply walking away.

At Risk (AR): the action

For At Risk, again with the customer’s permission, turn off the appliance or installation, attach an At Risk warning label, issue a warning notice, and advise that it must not be used until the fault is put right. The difference from ID is urgency and framing: there is no present emergency, so the emphasis is on preventing use until repair rather than on emergency escalation. If the customer refuses to let you turn it off, you advise and record — you cannot compel them, but you make the risk and the advice unmistakable.

NCS: a separate record of a safe standards shortfall

NCS is outside the current GIUSP. A safe shortfall can still be recorded: you record the defect, inform and advise the customer that the installation is below current standards and why, and recommend it is brought up to standard — but the appliance may stay in use because it is safe now. A classic exam trap is over-classifying a purely cosmetic or historic non-conformity as At Risk. If it is safe today and would not become dangerous in use, it is NCS.

Labels, warning notices and the paperwork

• A warning notice (the industry warning/advice notice) records the defect, the classification and the action taken. One part is left with the customer or on the appliance; you keep a copy. Being able to say what a warning notice is and who gets it is common in questions.
• The physical warning label is attached to the appliance or installation so the danger is visible to anyone who approaches it, not just the person who took the paperwork.
• Turning off or disconnecting always needs the customer’s permission first — this single rule underpins the "what if they refuse" branch of most scenarios.
• RIDDOR reporting is a separate legal assessment. Registered engineers must report dangerous gas fittings that meet the statutory criteria; do not assume every ID or AR finding is automatically reportable. Making safe takes priority, then follow the applicable reporting requirements.

Worked scenarios: classify then act

• An open-flued heater is spilling combustion products into the room while it runs. Danger now → Immediately Dangerous: with permission turn off and disconnect, label ID, issue a warning notice, and if permission is refused warn and call the gas emergency service.
• A boiler works normally but its flue passes too close to an opening window, so products could re-enter under some conditions. Not dangerous this moment but could be in use → At Risk: with permission turn off, label AR, warning notice, advise no use until corrected.
• An older but sound installation uses a fitting that today’s standard would site differently, with no danger now or in use → Not to Current Standards: record, inform and advise, appliance stays in use.
• You find a genuinely immediately dangerous appliance and the customer refuses to let you disconnect it. You do not simply leave: you warn them plainly of the danger, make your advice and the classification clear on the notice, and contact the gas emergency service. Refusal changes your options, not the danger.

Exam angle and common mistakes

• Getting ID and AR the wrong way round. Ask the "danger now?" question first and answer it honestly — present danger is ID, potential-in-use is AR.
• Treating NCS as "ignore it". NCS still means record, inform and advise; the appliance staying in use is a conclusion, not a licence to say nothing.
• Forgetting permission. Any answer that turns off or disconnects a customer’s appliance without noting that permission is needed is incomplete, and the "permission refused" branch is a favourite.
• Confusing GSIUR with GIUSP. The regulations are the legal duty; the procedure sets the ID and AR safety actions — name the right one for what the question asks.
• Leaving a known immediate danger connected. The safe answer always removes or contains the danger and escalates when permission is refused.