Gas detector with solenoid valve vs standalone detector: which to choose

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Why this question is key when choosing a gas detector

When a customer is considering the purchase of a gas leak detector, they often focus only on whether the device "works" and is "certified". In practice, however, at least equally important is a decision that is made before we even look at a specific model – namely, whether the detector will only warn (acoustically and visually signal the leak), or whether it will also actively intervene and physically close the gas supply using a solenoid valve. This decision significantly affects the level of operational safety, the cost of the solution, the complexity of installation, and what happens in the moment when no one is present in the room.

In this article, we will take a closer look at both concepts – how they work, their advantages and limitations, in which types of rooms they are actually used, what the wiring looks like, and what to pay attention to when choosing. We base our insights on practical experience with installations in apartments, single-family homes, boiler rooms, restaurants, and industrial facilities.

Principle of gas detector operation – common basis

Whether it is a standalone detector or a detector with a valve, the physical principle of detection is the same. The device contains a sensor (most commonly semiconductor or catalytic), which reacts to the presence of flammable gas in the air. When the gas concentration exceeds a set threshold (typically around 10% of the lower explosive limit, LEL), the electronics evaluate the situation as an alarm.

From this moment on, the paths of the two types of detectors diverge:

Standalone detector triggers an acoustic and visual signal, or optionally sends a signal to an external relay output (e.g., to an EPS system, home automation system, or a GSM module), but physically does nothing to the gas supply.
Detector with a solenoid valve in addition to signaling, automatically sends a command to close the electromagnetic valve installed on the pipe, thus physically cutting off the gas supply to the area.

Schematic principle – difference in reaction to alarm

This difference may seem trivial on paper, but in practice it determines whether a flammable gas concentration accumulates in an unoccupied room, or whether the problem is resolved automatically even before anyone becomes aware of the leak.

Standalone gas detector – what it offers and where it makes sense

A standalone detector, such as the Gas Detector AVANSA 100M, is a device primarily intended for signaling. After the set concentration is exceeded, it triggers a loud acoustic siren (typically around 85–100 dB near the device) and a blinking LED signal. Many models also have a normally open relay output, which can be connected to an external device – for example, to an existing solenoid valve that is part of an already implemented gas piping system, to an EPS control panel, or to a GSM/Wi-Fi module to send an SMS or notification.

Advantages of a standalone detector

Lower purchase price – you don't pay for a solenoid valve that you may not need.
Simpler installation – it is sufficient to connect the power supply (230 V or 12/24 V depending on the model), there is no need to interfere with the piping system.
Suitable where the space is constantly occupied by staff who can react to the alarm immediately (e.g., an attended boiler room, a restaurant kitchen during operation).
Can be supplemented with an external valve via the relay output if the need for automatic closing is later identified.

Disadvantages and risks

Without human intervention, the gas leak will not stop – if no one is present or the signal is not heard (e.g., at night, in a basement, in a remote boiler room), the gas continues to leak.
In the case of a power failure or lack of supervision, the alarm may remain unreacted for a longer period.
In buildings without permanent staff (recreational cabins, warehouses, technical rooms without personnel), a purely signaling solution is insufficient in terms of real safety.

Gas detector with a solenoid valve – active protection

Solutions such as Gas Detector AVANSA 100M + solenoid valve G1/2" DN15, AVANSA 100M + solenoid valve G3/4" DN20, or AVANSA 100M + solenoid valve G1" DN25 combine the detection unit with an electromagnetic valve mounted directly on the gas piping system. In the moment when the detector evaluates an alarm situation, it sends a command and the valve closes – physically cutting off the gas supply to the protected zone, regardless of whether a person is present in the room.

How the solenoid valve works in this setup

The solenoid valve is in an open state during normal operation (normally closed after power loss, thus safely closing both during a power outage and during an alarm signal – the exact behavior depends on the type of valve, typically a valve that automatically closes when power is lost is used). This means double protection: it closes not only during gas leak detection, but also during a power outage, which is a desirable behavior from a safety perspective – the system will always lean towards safety in the case of any failure (so-called fail-safe principle).

Connection diagram of a gas detector with a solenoid valve

Advantages of a detector with a solenoid valve

Active protection without the need for human intervention – works even in unoccupied areas, at night, during holidays.
Fail-safe behavior in case of power failure.
Meets the requirements of many boiler room and technical room projects where automatic gas supply shut-off is required in case of a fault.
Complete "out of the box" solution – the detector and valve are factory-tuned as a functional unit, no need to worry about compatibility of components from different suppliers.

Disadvantages and what to be careful about

Higher purchase price compared to a standalone detector.
More complex installation – the valve is mounted directly into the piping system, which requires gas supply shutdown, working with sealing connections (most commonly hemp fiber with sealant or Teflon tape depending on the thread type), and a subsequent pressure tightness test.
It is necessary to select the correct valve size (DN) matching the diameter of the existing piping and gas flow – an incorrectly dimensioned valve can cause an unacceptable pressure drop.
Closing the gas supply can cause operational outages (e.g., boiler shutdown) in case of a false alarm, so it is important to have a high-quality sensor with minimized risk of false alarms – we elaborate on this topic in detail in the article on common faults and false alarms of gas detectors.

Comparison of both solutions in a clear table

Criterion	Standalone detector	Detector + solenoid valve
Reaction to alarm	Sound + light	Sound + light + closing the supply
Works without supervision	No (safety depends on human reaction)	Yes, automatically
Piping intervention	Not necessary	Yes, valve installation on the piping
Purchase price	Lower	Higher
Installation complexity	Low	Moderate to high (gas fitter required)
Fail-safe in case of power failure	No	Yes (with the right type of valve)
Typical use	Occupied areas, supplementary solution	Boiler rooms, unoccupied areas, high-risk operations

When a standalone detector is sufficient – real-life scenarios from practice

From our experience with implementations, we know that a standalone detector is most often suitable in these situations:

Kitchen of a restaurant or public catering business during opening hours, where staff is always present and able to react immediately – turning off the main shut-off valve, ventilating the area, and calling for service.
Apartment or family house, where the owner wants a cheaper solution and is willing to rely on the fact that in case of a leak, they will be at home and able to manually intervene (closing the main valve at the gas meter).
Supplementary signaling in areas where automatic gas shut-off is already handled centrally by another system (e.g., one central valve for the entire building) and the detector serves only as an additional signal for the staff or for connection to an existing EPS system.

Real-life example: in a smaller bakery with gas ovens, we installed a Gas detector AVANSA 100M without a valve, because the operation was continuous with staff on site and the investor already had a separate manual central shut-off at the main pipe inlet. In this case, it made sense to save on the component cost and rely on the staff.

When to clearly choose a detector with a solenoid valve

On the other hand, there are many situations where I would not recommend a standalone detector without a valve at all:

Unmanned boiler rooms – gas boiler rooms in apartment buildings, administrative buildings, or industrial facilities where no one is present 24/7. In such cases, automatic closing of the gas supply is practically essential and in many cases also a project or standard requirement.
Recreational properties and cottages, where the owner is not present for most of the year and a gas leak (e.g., from the piping to the gas boiler or water heater) could go unnoticed for weeks.
Warehouses and technical rooms with gas appliances, where staff only occasionally move around.
High-risk areas – for example, garages with gas cylinders, LPG (propane-butane) boiler rooms, where due to the higher density of the gas, accumulation near the floor and the risk of explosion is higher.
Nocturnal operations without staff – restaurants and businesses that close at night and leave the kitchen unattended, but gas piping remains under pressure.

Real-life example: during the renovation of a boiler room in an apartment building with two condensing boilers, we installed AVANSA 100M with a solenoid valve G1/2" DN15 directly on the supply to the individual boilers, because the boiler room was unmanned and the maintenance technician required automatic gas supply shut-off in case of a leak according to the project documentation. In the case of a larger diameter of the main piping (e.g., a shared boiler room with higher capacity and larger piping), a valve of G3/4" or G1" is selected, depending on the actual gas flow and piping dimensioning – we elaborate on this topic in more detail in the article on selecting the correct solenoid valve for a detector.

Detector placement according to gas type – why it also affects the choice of solution

Regardless of whether you choose a standalone or active system with a valve, the functionality of the entire solution depends on the correct placement of the sensor. Natural gas is lighter than air and rises upwards, so the detector is mounted in the upper third of the room, near the ceiling. Propane-butane is heavier than air and accumulates near the floor, so the detector is placed low, usually within 30 cm above the floor.

Detector placement diagram according to gas type

This rule applies equally to standalone detectors and models with a solenoid valve – the valve only reacts to what the sensor tells it, and a poorly placed sensor can signal with a significant delay or not at all. A detailed guide on calculating the mounting height and distance from the gas source can be found in the article on detector placement and mounting height according to gas type.

Installation procedure – what differs with a valve-based solution

With a standalone detector, installation is simple – mounting on a wall or ceiling at the correct height, connecting power (230 V from an outlet or fixed connection, or 12/24 V), and in case of need, connecting the relay output to an external device. It is usually a task that a skilled electrician or experienced DIYer can handle, of course respecting the manufacturer's placement instructions.

When using a solution with a solenoid valve, the procedure is more complex and should be carried out by a qualified person authorized to work on gas equipment:

Step-by-step installation procedure for a detector with a solenoid valve

After installation, a leak tightness test (e.g., using soapy water or a manometric test) and a functional test always follow. The functional test involves simulating an alarm to verify that the valve actually closes the gas supply within the required time (typically within a few seconds of detection). A complete detailed guide for installation, including wiring diagrams, can be found in a separate article on the installation and connection of a gas detector with a solenoid valve.

Legislation and technical standards – when is the valve mandatory

In Slovakia, the design of gas equipment is based on STN EN standards and technical gas rules (TPP), which in many cases require automatic closure of the gas supply in the event of a leak or pressure drop when dealing with boilers of a certain capacity or in unattended operation. Specific requirements vary according to the boiler's capacity, the type of building (apartment block, industrial facility, public building), and whether it is a new build or a renovation.

In practice, this means that the designer or gas equipment inspector often directly prescribes a detector with an automatic valve as part of the boiler's safety system. We therefore recommend consulting the designer about the requirements for larger projects (apartment block boilers, commercial buildings) before purchasing to avoid situations where a valve must be purchased additionally, which could have been ordered as part of a complete set.

Selecting the correct type and size of solenoid valve

If you decide on a solution with automatic closure, it is important to choose the correct size (DN) of the valve according to the diameter of the existing pipe and the gas flow required for the appliance or group of appliances. In our range, you will find three common variants:

G1/2" DN15 – suitable for smaller operations and low-flow distribution, typically for home boilers and smaller appliances.
G3/4" DN20 – medium size, a common choice for larger home boilers or smaller industrial spaces.
G1" DN25 – larger size for higher flows, typically for apartment block boilers or industrial applications with higher appliance capacity.

An incorrectly undersized valve can cause an unacceptable pressure drop and insufficient appliance performance, while an oversized valve unnecessarily increases cost and complicates installation for smaller systems. A detailed procedure for calculation and selection according to pipe diameter is discussed in an article on selecting the correct solenoid valve for a detector.

AVANSA 100M vs AVANSA 150MC – difference in the context of this topic

Alongside the question of "with a valve or without," it is also important to consider the detector unit itself. The basic Gas Detector AVANSA 100M is intended for standard applications in homes and smaller facilities. The more advanced Detector AVANSA 150MC offers extended features (e.g., different signal processing, different output configurations), and is suitable especially where a more robust solution or specific integration into existing technology is required. A detailed comparison of all AVANSA models, including recommended use, can be found in a separate article comparing AVANSA 100M, 150MC, and 200M.

Practical examples from customer orders

Apartment in an apartment block with a gas boiler

A common scenario – a household with a gas boiler for heating and hot water. If the apartment is permanently occupied and the owner wants basic protection, a standalone Gas Detector AVANSA 100M installed in the kitchen or near the boiler is usually sufficient. However, if the apartment is often unoccupied (e.g., due to business trips or second home status), we recommend considering a solution with a valve to automatically stop any leak even in the owner's absence.

Detached house with its own basement boiler room

Boiler rooms in the basements of detached houses are typical places for leaks due to aging seals or damaged piping. Since basements are usually visited only occasionally, we almost always recommend a combination of a detector and a solenoid valve in these cases, for example AVANSA 100M + valve G1/2" DN15, which can automatically close the supply before anyone even enters the basement.

Apartment block boiler room with central heating

For larger boilers with higher capacity and larger pipe diameters, a valve with a larger size is usually selected, for example AVANSA 100M + valve G1" DN25. In these cases, automatic closure is practically always part of the project documentation and is also required by the inspector.

Restaurant kitchen with night-time closing

During operating hours, there is staff in the kitchen, so theoretically a standalone detector would be sufficient. However, since the kitchen is closed at night and the gas lines remain under pressure, we recommend a combined solution with a valve – in the case of a leak during closed hours, the supply is automatically interrupted, eliminating the risk of gas accumulation until morning.

Industrial workshop with gas burners

In larger industrial spaces with multiple appliances (burners, dryers), it is common to install multiple detectors at once, each of which can control a separate valve on its own branch of the supply, or all together close the main inlet valve of a higher size. This configuration requires a detailed project solution and usually goes beyond the scope of a simple do-it-yourself installation.

Costs and return on investment

A solution with a solenoid valve is more expensive at the purchase price than a standalone detector – the difference is usually in the range of tens of euros more, depending on the valve size. However, this investment should be compared not with the price of the detector alone, but with the potential damage caused by an unresolved gas leak – from property damage due to explosion, through health risks, to insurance complications (insurance companies often investigate whether the project documentation and safety measures were followed in the case of a damage event caused by a gas explosion). Therefore, we consider the investment in a valve to be clearly justified in boiler rooms and unattended areas, even though it increases the initial costs by tens of euros.

Maintenance and testing of both types of solutions

Regardless of which type you choose, the detector sensor has a limited lifespan (usually several years depending on the sensor type and manufacturer) and requires regular functional checks. In the case of a solution with a valve, it is also necessary to regularly verify that the valve actually moves and closes – mechanical components can "freeze" in one position over time, especially during long periods of inactivity. We therefore recommend performing a full functional test of the entire sensor-electronics-valve chain once a year, not just checking the sensor itself. A detailed maintenance schedule, cleaning and calibration can be found in the article on maintenance, calibration and sensor lifetime of gas detectors.

Common questions

Can a solenoid valve be purchased later for an existing standalone detector?

In most cases, yes, provided the detector has a dry contact relay output intended for controlling an external device. However, it is necessary to verify the compatibility of the output with the specific type of valve and to ensure professional installation of the valve into the pipe, including a tightness test. It is usually simpler and more reliable to directly choose a complete set where the components are factory-tuned as a functional unit.

Will a solenoid valve stop a gas leak that occurs before the valve itself (e.g., at the main shut-off)?

No, the valve can only close the branch of the supply on which it is physically mounted. If a leak occurs before the point of installation of the valve (e.g., directly at the main supply to the building), it is necessary to have a safety element there as well, or to handle the situation manually with a main shut-off valve.

Must a solenoid valve always be of the type that closes in the event of a power failure?

From a safety perspective, a fail-safe version is clearly recommended, i.e., a valve that automatically closes in the event of a power failure. This behavior ensures that in the event of a power grid failure, the gas supply remains safely interrupted, and not left open without control.

Is it mandatory to have a detector with a solenoid valve in a regular apartment?

In most apartments, it is not legally mandatory to have automatic closing, it is more of a recommendation for increased safety. However, in boiler rooms and unattended technical areas, this is often required by current standards and project documentation – specific requirements should always be discussed with the designer or gas inspection technician.

How quickly can the valve close the gas supply after detecting a leak?

It usually takes the order of seconds from the moment the electronics evaluate the alarm condition. The exact time depends on the specific model and the sensitivity setting of the sensor – higher sensitivity means a faster reaction, but also a slightly higher risk of false alarms, unless the sensor is properly placed and maintained.

Is a solution with a valve worth it even in a smaller apartment with only one gas stove?

In a small, permanently occupied apartment with a simple appliance (e.g., only a stove without a gas oven), a standalone detector is usually sufficient in practice, since the risk of a long-term unresolved leak is lower due to the presence of residents. However, if it is a rarely used apartment or a more sensitive situation (children, elderly or disabled residents), we recommend considering a combined solution for greater certainty.

Summary – how to decide

The choice between a standalone detector and a detector with a solenoid valve is not a question of "what is better" in general, but a question of what risk is actually present in the given space and who (or what) is able to react to the alarm. In areas that are permanently occupied and where staff can act immediately, a standalone detector such as the AVANSA 100M can represent a sufficient and economically advantageous solution. In areas that are not permanently occupied, such as boiler rooms, warehouses, recreational buildings or businesses with night breaks, we clearly recommend investing in a complete solution with a solenoid valve, which is able to react automatically, without waiting for human intervention. When choosing the specific valve size and detector model, it is worth consulting with a specialist, or using further articles in this Knowledge Center devoted to selection according to gas type, placement and installation.

Do you have a question about this topic?

Are you unsure or dealing with a specific situation in your home? Write to us – we are happy to help.