When it comes to carbon monoxide and the central heating boiler, obligations and recommendations get mixed up. Many residents think annual servicing is a legal requirement and that a carbon monoxide alarm is mandatory just like a smoke alarm; the opposite is closer to the truth. What the law does regulate strictly is who may work on a gas-burning appliance. This article sets out, topic by topic, what the Besluit bouwwerken leefomgeving (Bbl, the Dutch Building Decree) says, what the fire service and the GGD (the Dutch municipal public health service) advise and what you can check yourself. It is general information; the manual for your appliance and your alarm takes precedence over general rules of thumb.
Smoke alarms: mandatory, on every storey
Since 1 July 2022 the smoke alarm requirement has applied to all homes, including existing ones. Article 3.117(1) Bbl prescribes that a residential function must have a smoke alarm complying with EN 14604 on every storey with a habitable room, or with an enclosed space through which an escape route runs between a habitable room and the exit of the home. In plain English, as the Rijksoverheid (Dutch central government) summarises it: there must be a smoke alarm on every floor with a living room, bedroom or kitchen; a loft or cellar that you only use for storage or for drying washing does not need one. Stricter requirements have applied to new builds for longer (Article 4.211 Bbl): smoke alarms in accordance with NEN 2555, so connected to the mains and interlinked, in every habitable room and on the escape route. In a major renovation, your municipality may apply the new-build requirements to the renovated part; ask about this when you apply for the permit.
The owner must install the smoke alarms; if you rent, that is the landlord, although as a tenant you can be expected to check and replace the battery. In a flat with a VvE (owners' association), you install the alarms in your own home yourself; the requirement does not apply to communal areas such as the stairwell. The municipality enforces the rules. Practical advice from the Rijksoverheid: mount the alarm on the ceiling, preferably in the hall, at least fifty centimetres from a wall or corner and thirty centimetres from a light fitting, not near ventilation openings or a heater, and choose an alarm with a battery that lasts ten years.
Carbon monoxide alarm: not mandatory, but strongly recommended
The Bbl contains no requirement for a carbon monoxide alarm, not for existing homes and not for new builds either. During the consultation on the Bbl there were calls to include such a requirement, but the legislator chose a different route: the certification of installers (see below). The fact that an alarm is not mandatory does not make it superfluous. The fire service and the GGD advise everyone with a combustion appliance at home to install several carbon monoxide alarms, expressly including with a modern, room-sealed central heating boiler: in every room where an appliance is located and in rooms where people spend a long time, such as the bedroom. If you live in a walk-up flat or apartment building with a shared flue, an alarm is even more important, because carbon monoxide can also come in from the neighbours' home.
Only buy an alarm with the standard NEN-EN 50291 on the packaging; the fire service recommends one that lasts five to ten years, and the Consumentenbond (the Dutch consumers' association) publishes a list of tested alarms. Write the installation date and the replacement date on the alarm. The test button only checks the battery and the alarm sound, not whether the sensor still measures carbon monoxide; so after the lifespan specified by the manufacturer, you replace the alarm even if it still beeps during a test. According to the fire service, a combined smoke and carbon monoxide alarm is only suitable in the room where the combustion appliance is located; elsewhere, smoke and CO alarms hang at different heights and you choose two separate alarms.
Where should you hang the CO alarm?
Carbon monoxide is almost as heavy as air and mixes evenly; so it does not rise like smoke, but it does not sink to the floor either. The fire service therefore gives two different placement recommendations, based on research by the Brandweeracademie (the Dutch fire service academy).
- In the room with the combustion appliance (central heating boiler, gas water heater, gas fire, wood stove): on the ceiling, because the warm air around the appliance carries the carbon monoxide upwards first. At a horizontal distance of one to three metres from the appliance, centrally in the room, at least thirty centimetres from the walls and not next to air inlets or outlets or other objects on the ceiling. With a sloping ceiling, mount the alarm on the sloping part, at the same distance from the appliance.
- In rooms without an appliance, such as the bedroom: at breathing height, that is the height at which you sleep or sit, not behind curtains or cupboards and not next to ventilation grilles.
- Never directly above a cooker, next to air inlets or outlets or hidden behind furniture.
If the manual for your alarm differs from this, follow the manual or ask the supplier for an explanation. If the alarm goes off: warn the people in your household, go outside and call 112; do not go back inside to take a look.
Recognising carbon monoxide poisoning
Carbon monoxide is odourless and colourless. The first symptoms resemble flu: headache, nausea, dizziness, tiredness, drowsiness, confusion, a rapid heartbeat and vomiting. According to the GGD, two features distinguish poisoning from flu: the symptoms ease as soon as you are outside and everyone present develops symptoms, although these can differ from person to person; pets also become ill. At higher concentrations, unconsciousness, permanent brain damage and death follow. According to the fire service, an average of five to ten people die in the Netherlands each year and hundreds end up in hospital; the Onderzoeksraad voor Veiligheid (the Dutch Safety Board) estimates the real number of victims to be three to five times higher, because the poisoning often goes unrecognised.
The chronic form is trickier: if you breathe in a small amount over a long period, you get vague and varying symptoms, from morning headaches to low mood and forgetfulness, while the alarm does not go off, because it only sounds at higher concentrations. If you have persistent symptoms that come on at home and ease outside, and you have a combustion appliance that burns regularly, discuss this with your GP and have the appliance checked. Ventilation is the first line of defence: the GGD and the fire service advise keeping a vent open or a window ajar day and night.
Boiler servicing: how often, and who is responsible?
There is no legal servicing obligation for the owner-occupier of a central heating boiler. There are, however, three other sources of obligation or advice. Firstly the manufacturer: the installation instructions give a servicing interval, often annually or every two years, and the manufacturer's warranty may lapse if this is not followed. Secondly the insurer: some buildings or contents insurance policies contain a clause about periodic servicing of heating installations; check your policy conditions. Thirdly the safety advice: the fire service and the GGD recommend an annual check by a certified tradesperson, while the Rijksoverheid says at least once every two years. With an older boiler, an open-flued appliance or intensive use, once a year is sensible; with a young, room-sealed high-efficiency (HR) boiler, follow the manufacturer's interval. Put the date in your maintenance calendar, preferably in spring or summer, when installers have capacity.
If you rent, servicing the central heating installation is a matter for the landlord: it is not one of the minor repairs that are the tenant's responsibility. As a tenant, you can therefore require the landlord to have the boiler serviced periodically by a certified company. In an apartment complex, the VvE or the landlord is responsible for maintaining the shared flue; the Rijksoverheid advises residents to ask for proof that the flue has been checked and is safe, and, when the boiler is replaced, to check in advance whether the new appliance is suitable for the shared flue.
Since 1 April 2023: only a CO-vrij certified company
This is the part that is firmly laid down in law. Article 6.45 Bbl stipulates that installing, repairing and servicing a building-related gas-burning appliance and the associated flue and combustion air supply, and then commissioning and releasing the appliance for use, may only be carried out by a certificate holder. The rule is aimed at the person carrying out the work as well as the person having it carried out (paragraph 1): a resident who lets a non-certified odd-job man work on their boiler is also in breach themselves and risks enforcement action by the municipality. It covers all gas appliances for heating or hot water: central heating boilers, gas water heaters, gas storage water heaters, back boilers with gas fires and decorative gas fires. Not covered by the ban are gas cookers and cooking appliances, stand-alone gas heaters and patio heaters, and work on gas pipes, radiators and expansion vessels. You may continue to carry out simple tasks yourself: using the reset button, topping up the central heating water, pulling out the plug, replacing batteries, setting the thermostat.
This is how you check a company. Certified companies are listed in the public register gasverbrandingsinstallaties (register of gas combustion installations) of the Toelatingsorganisatie Kwaliteitsborging Bouw (TloKB, the Dutch building quality assurance approval body); search by company name or location and check the status of the certificate and which certification body is listed. A certified company displays the prescribed CO-vrij logo on quotes, its website and company vehicle (Article 6.47 Bbl), and the engineer carries an ID card with that logo, which you may ask to see. If a newly certified company is not yet in the register, this can take a few working days; in that case ask for the certificate. If, during their work, the engineer measures too high a concentration of carbon monoxide in a room where people may be present, they must report this immediately to you, to the municipality and to their certification body (Article 6.46 Bbl). If you have a complaint about the work, you can turn to that certification body, which is listed with the company in the register. You can read which tradesperson to call for what in Plumber, installer or central heating engineer; what sets the CO-vrij logo apart from voluntary quality marks is explained in Quality marks in construction explained.
Open-flued combustion appliances and ventilation
An open-flued appliance, such as a kitchen gas water heater without a flue, an old open gas heater or an open fireplace, draws its combustion air from the room in which it is located and sometimes also releases its flue gases there. That makes it the biggest risk factor in the home: if there is too little fresh air supply, the gas burns incompletely and carbon monoxide is produced, and a blocked or leaking flue brings the gases back into the room. Warning signs mentioned by the fire service: a yellow-orange instead of blue flame, soot or rust on the appliance, condensation on windows and walls during use, and a flue with many bends or horizontal sections. A heating installer or central heating engineer with a CO-vrij certificate can assess the appliance; with an open-flued gas water heater, replacing it with a room-sealed appliance or an alternative without combustion is often the safest option, and the plumber can then adapt the hot water supply. Have the chimney of a wood or coal stove swept every year and have the connections checked.
Ventilation remains necessary in all cases, including with room-sealed appliances and certainly after insulation or draught-proofing work: what used to come in through gaps and cracks now has to come in through vents and ventilation facilities. Do not tape over vents in winter, and during a renovation have the ventilation of the room with the appliance included in the design. In short: smoke alarms are mandatory, a CO alarm is sensible, boiler servicing is a manufacturer's and safety recommendation, and work on the gas appliance is legally reserved for a certified company that you can look up in the register.