What it means when a gas engineer turns off your boiler

People often describe it as the boiler being “condemned”. The industry word is different, and the categories matter, because they decide whether you can keep using the appliance at all. This guide explains what the engineer is doing, why, and what your choices are.

The procedure behind it

Every Gas Safe registered engineer follows the Gas Industry Unsafe Situations Procedure, published by IGEM as IGEM/G/11 (Gas Safe Register, GIUSP PDF). It sorts problems into categories so that every engineer treats the same fault in the same way.

The three categories

Category	What it means	What the engineer does
Immediately Dangerous (ID)	A danger to life or property if left running	Disconnects it with your permission. If you refuse and it is natural gas, reports it to the gas emergency service
At Risk (AR)	Not dangerous this minute, but one or more faults could become dangerous	Turns it off with your permission and attaches a Danger Do Not Use label
Not to Current Standards (NCS)	Safe, but does not meet today’s standards	Tells you. Acting on it is your choice

Source: Gas Safe Register, warning labels.

Gas Safe Register explains that for an Immediately Dangerous natural gas installation, if you do not give permission to disconnect, the engineer reports it to the Gas Emergency Service Provider, which has legal powers to disconnect the gas and make the situation safe. In north London, that is Cadent (Cadent).

How “turned off” is done

The procedure sets an order. The engineer first turns off the gas isolation valve to the appliance. Only if that is not possible do they remove the electrical fuse. Only if neither is possible do they turn off the appliance control and fix a warning label to it. Turning the thermostat down or setting the timer to off does not count.

You will also be given a written warning notice describing the fault, the category and what was done. You will be asked to sign it.

Common reasons in north London homes

Some faults come up again and again in the housing around Crouch End, Hornsey and Muswell Hill, where many Victorian and Edwardian houses have been split into flats or extended.

Hidden flues in ceilings. Some converted and newer flats have boiler flues running through ceiling voids. If there are no inspection hatches, the engineer cannot see the flue joints. Since 1 January 2013, HSE says an engineer will advise that such an appliance is At Risk and, with permission, turn it off until hatches are fitted (HSE, flues in voids).

Flue terminals blocked by building work. A loft conversion, dormer or rear extension can leave an existing flue ending too close to a new window, or under a new roof. See our post on moving a boiler into a loft conversion.

Spillage from gas fires. An old gas fire in a Victorian chimney can fail a spillage test if the chimney is blocked or not drawing. That means fumes are coming back into the room.

Poor combustion. Flue gas analyser readings outside the manufacturer’s limits can point to a fault that could produce carbon monoxide.

Gas escapes. A failed tightness test on the pipework, or a smell of gas at a joint.

What to do next

1. Leave it off. Do not try to relight it or remove the label.
2. Read the warning notice. It will say what the fault is and the category.
3. Ask what fixes it. Some At Risk faults are a part or a small repair. Others, such as an unsafe flue route, need more work.
4. Get it repaired by a registered engineer. You can use the engineer who found it or another one. Check their Gas Safe ID card covers the appliance. Our boiler repair page explains how that visit works.
5. Landlords: record the follow up. HSE says the gas safety record should be issued even if faults are found, and the landlord adds the repair action to it afterwards (HSE).

If you are a tenant

If an engineer turns off the boiler in a rented flat, tell your landlord or agent in writing the same day. HSE says landlords must take action to make sure gas appliances are safe, and that repairs from wear and tear are the landlord’s responsibility (HSE). Keep a copy of the warning notice.

Carbon monoxide

Many At Risk and Immediately Dangerous faults are about carbon monoxide. If anyone in the home has had headaches, dizziness, nausea or tiredness that ease away from home, mention it. The NHS advises calling 999 or going to A&E if symptoms are severe. Fit a carbon monoxide alarm in the room with the boiler. See carbon monoxide alarms.

Book a check before it comes to this

Most unsafe situations are found during routine visits. A gas safety check from London Gas Engineers, in Crouch End or anywhere across north and east London, looks at every gas appliance and flue. For landlords, our guide to what a landlord gas safety check includes explains the full process.