Suspected Gas Leak in Brussels: Warning Signs to Recognise and What to Do Immediately

A gas leak doesn't always announce itself dramatically. More often than not, it shows up through small, discreet signals: an unusual smell, a faint noise near a pipe, a plant withering for no apparent reason. At DPS Chauffagiste, we regularly respond to situations in Brussels where these warning signs were spotted too late, or misread. Knowing how to recognise them and adopting the right reflexes can make all the difference to a household's safety.

Signs that should raise the alarm

Natural gas distributed to Brussels homes is, in its pure state, odourless. Suppliers deliberately add a substance called mercaptan, which gives it that distinctive smell of sulphur or rotten eggs. It is precisely this smell that should immediately grab your attention. If this odour lingers in a room, near the meter, the boiler or a gas cooker, it should be treated as a serious warning sign, and you should act without waiting for further confirmation.

Other signs may accompany or precede this smell:

• A hissing sound or continuous noise near a pipe, a fitting or the gas meter, especially if it's new and localised.
• An abnormal flame on a cooker or boiler: a healthy gas flame is blue and steady; if it turns yellow, orange or flickers, this may indicate a combustion problem linked to a leak or a supply fault.
• Vegetation that is turning yellow or dying in a localised and unexplained way, particularly above or near a gas pipe buried in a garden or outdoor space. Gas escaping into the soil deprives the roots of oxygen and can cause this targeted dieback.
• Unusual physical sensations among occupants: headaches, dizziness, nausea or unexplained drowsiness, especially if several people in the same household experience the same symptoms at the same time. These signs can also point to carbon monoxide poisoning, a separate risk but one often linked to poor combustion or insufficient ventilation.
• Freshly disturbed earth or a visible bubble in a puddle outdoors, near a buried pipe, can also betray an underground leak.

None of these signs on its own is absolute proof, but their appearance, whether alone or combined, calls for immediate vigilance and the right course of action.

What to do straight away

When a gas leak is suspected, acting quickly and calmly matters just as much as getting the steps right. Here is the order of priorities to follow.

Do not create any sparks

Natural gas is flammable and can ignite from the smallest spark. It is therefore essential to:

• avoid flipping an electrical switch, or turning a light on or off;
• avoid using a doorbell, mobile phone, lighter or any electrical appliance in the affected area;
• avoid lighting a flame, candle or cigarette;
• avoid plugging in or unplugging an electrical appliance nearby.

These seemingly harmless actions can be enough to trigger ignition if the gas concentration in the air is high enough.

Ventilate immediately

Open the doors and windows of the affected room as wide as possible, and ideally throughout the whole property, to allow the gas to disperse into the outside air. Good ventilation quickly reduces the gas concentration and limits the risk of a dangerous build-up.

Shut off the gas supply if it's accessible

If you know where the main shut-off valve is, usually located before or at the meter, turn it off without forcing it. This simple action stops the gas supply at the source and limits the scale of the leak while waiting for a professional to intervene. If it isn't easily accessible or you're unsure of its location, don't waste time looking for it: evacuating the premises remains the priority.

Evacuate the building

Leave the property with the other occupants, leaving doors and windows open behind you if possible. If you live in an apartment block, warn your immediate neighbours, as a leak may affect a shared rising main or several homes.

Contact the relevant services

Once outside and safe, contact the gas emergency service of your network operator without delay — Sibelga for the Brussels-Capital Region — whose emergency number is available 24/7. If in doubt about the severity of the situation, or if you notice a strong smell, a loud noise or signs of poisoning, also call the emergency services on 112. These services are trained to pinpoint the exact source of a leak and secure the premises if necessary.

Why you should never try to fix it yourself

Faced with a suspected leak, it can be tempting to check the source of the problem yourself, tighten a fitting, or relight the boiler once the smell has faded. This is precisely what you should not do.

A gas installation must comply with precise safety standards, covering pipe sizing, the tightness of fittings and the ventilation of rooms. A fault invisible to the naked eye, a hairline crack or a worn seal, can be enough to cause a leak, and only specialised equipment can locate it with certainty. Reopening a supply or restarting an appliance without this diagnosis exposes you to a real risk, both of explosion and of carbon monoxide poisoning in the event of poor combustion.

This is also a legal requirement: in Brussels, gas installations and heating appliances must undergo regular checks and servicing carried out by approved technicians. After a confirmed or suspected leak, only a professional intervention can confirm that the installation is safe again.

The role of the approved professional after a leak

When we respond following a suspected leak, our approach always follows the same rigorous logic:

1. Precise detection using an electronic gas detector, which locates the exact source of the leak, whether at a fitting, a valve, a pipe or the appliance itself.
2. A full inspection of the installation, including the boiler, flue ducts, connections and safety components, to make sure no other weak point remains.
3. Repair or replacement of faulty components, in line with current standards.
4. Combustion and tightness checks before putting the installation back into service, to ensure it operates correctly and safely.
5. A compliance certificate, which allows you to reopen the installation with confidence and keeps a record of the work carried out.

This methodology is not an administrative formality: it genuinely protects the occupants of the home against a risk that can remain invisible after a superficial first repair.

Prevention rather than cure

The best protection against a gas leak remains regular servicing of the installation. The annual boiler service, compulsory in Brussels, is precisely what allows signs of wear to be caught before they become a problem: a weakened seal, slight corrosion, a loosely tightened fitting. These regular checks are also an opportunity to verify that the flue system is working properly, a key element in preventing carbon monoxide poisoning.

Installing a carbon monoxide detector in rooms fitted with a combustion appliance is also a simple and inexpensive precaution, complementing your sense of smell when it comes to gas. The two risks are different but often linked: poor combustion can both signal an installation problem and generate CO, an odourless and therefore particularly insidious gas.

DPS Chauffagiste, by your side whenever you're in doubt

Whether you've noticed a suspicious smell, an unusual noise near your meter, or simply have doubts about the state of your installation, don't wait for the situation to get worse. Our team of approved heating engineers responds across Brussels to quickly diagnose any suspected leak, secure your installation and support you through the process of getting it back into service. Gas safety leaves no room for guesswork: a simple phone call can save you a great deal of trouble.