CO Detector: Review & Recommendations

Carbon monoxide is a toxic gas produced by barbecues, fireplaces, radiant heaters or cigarettes. Since it is colourless and odourless, you can hardly recognise it. With CO detectors, however, you will be alerted as soon as a critical level of CO concentration in the room is exceeded.

Our big CO detector test 2020 is designed to help you find the best CO detector for you. We have compared the standard and wireless CO detector, as well as CO detectors for the hearing impaired, gas detectors, portable CO detectors and CO smoke and/or heat detector combinations and listed the advantages and disadvantages of each. This should help you with your purchase decision.

The most important facts in brief

  • Carbon monoxide is a poisonous, colourless and odourless gas which is produced during the combustion of carbon-containing substances. Even low concentrations can lead to carbon monoxide poisoning without being noticed.
  • CO detectors alert you as soon as the CO concentration in the room exceeds a certain critical level, which can be harmful to you.
  • CO warning devices usually only detect carbon monoxide. There are special gas detectors for gases such as butane, propane or methane and separate warning detectors for carbon dioxide.

CO detector test: Favourites of the editorial team

  • The best CO detector with 10-year battery
  • The best CO detector with LCD display
  • The best CO detector with temperature display
  • The best CO detector with acoustic display

The best CO detector with 10-year battery

The Ei Electronics Ei208D CO alarm is a sensitive, medium size alarm for use in the home, motorhome and boat.

As the CO detector is mainly designed for wall mounting, the product weight is rather secondary. With its 120 x 105 x 45 mm, the device is not too large and, thanks to its discreet appearance, does not appear to be a foreign object in the room.

The fixed lithium battery eliminates the need to change batteries and the resulting battery waste. In addition, it reliably supplies the warning indicator with power over its entire service life of 10 years. Ten years is currently the highest lifetime currently available for carbon monoxide sensors.

The operating temperature range of -10 – 40 °C also covers the frost range. This means that the warning detector can still operate in outside cellars or other very cold rooms.

The best CO detector with LCD display

The Heiman CO detector has a state-of-the-art sensor and a high-quality chipset that detects dangerous carbon monoxide concentrations without false alarms with a service life of over 10 years. The battery included in the scope of delivery has a service life of 5 years.

After an alarm, the alarm indicator can also be reset to monitoring mode. The alarm tone is very loud at 85 dB and cannot be overheard in an emergency. The outer housing of this detector is made of high-quality, environmentally friendly and flame-resistant ABS plastic.

The best CO detector with temperature display

This Smartwares CO detector has a display that alternates between the carbon monoxide value in ppm and the temperature. The detector has a durable electro-chemical sensor that will give you a reliable 7 year warning of carbon monoxide.

The recommended operating temperature is 0°C to 40°C. There is a test button for function tests and the digital display allows easy reading. Battery, plugs and screws are included, so the detector can be mounted quickly and easily.

The best CO detector with acoustic display

This Smartwares CO detector gives you a reliable early warning of carbon monoxide poisoning for over 10 years. Included in the delivery are plugs, screws and batteries with a life span of 3 years.

The long-life sensor of the detector works electro-chemically and does not cause false alarms. The alarm tone reaches approximately 85 dB and is therefore not audible. The test button for function test on the front is easy to reach.

Advisor: Questions you should consider before buying a CO detector

What is carbon monoxide anyway?

Carbon monoxide is a colorless, odorless, tasteless, toxic gas with a density similar to that of air. It therefore spreads rather slowly in the room.
In technical terminology, the term carbon monoxide or carbon monoxide is more commonly used. This chemical compound of carbon and oxygen with the structural formula CO is a colourless, odourless and tasteless poisonous gas and therefore particularly dangerous. In your sleep you do not notice the gas and can suffocate.
Carbon monoxide has a density similar to that of air and therefore spreads very slowly in the room. Since it is slightly lighter than air, it still rises slowly. It is also combustible and burns with oxygen with a blue flame.
The concentration of particles or the proportion of carbon monoxide is given by the English expression ppm (parts per million). In English: The millionth part, just as a percentage is the hundredth part of something. 50 ppm thus corresponds to a concentration of 0.005% of the room air.

How is carbon monoxide produced and what are its sources?

In general, carbon monoxide is always produced when something is burned. Grills, fireplaces, radiant heaters but also cigarettes are possible sources of carbon monoxide.
Carbon monoxide is formed when carbonaceous substances such as natural gas, biogas, light petrol, heavy fuel oil, coal or biomass are incompletely burned when there is insufficient oxygen supply.
The concentration in residential buildings is usually between 0.5 and 5 ppm. In rooms with gas burners, however, the CO concentration can easily reach 15 ppm. Even in rooms with a chimney, there should normally be no higher concentrations if there is sufficient chimney draught, as the gas evaporates with the warm air from the chimney.
Incorrectly functioning heating and exhaust air systems and defective or improperly maintained equipment can be sources of carbon monoxide. If the flue of a chimney or stove is unable to expel the CO gas, a backflow occurs and the room fills up with carbon monoxide unnoticed. The fume cupboard does not even have to be faulty, it is sufficient if, for example, a bird or wasp nest blocks the exhaust duct.
In addition, carbon monoxide is produced when barbecuing with charcoal and wood fires in general. Propane gas fired radiant heaters or similar emit carbon monoxide gas. Other sources of carbon monoxide are gas stoves, the combustion of wood pellets, car exhaust from connected garages and all kinds of ventilation equipment and generators powered by combustion engines.

But cigarette and shisha smoke also contains carbon monoxide. Just ten smoked cigarettes increase the CO concentration in a 30 m³ room by 22 ppm. The Federal Ministry for Risk Assessment (BfR) explicitly points out a high CO concentration in shisha smoke in an assessment.

Symptoms and consequences of carbon monoxide pollution/poisoning

If you breathe a high concentration of the gas, it will quickly become fatal. But even if you are exposed to a low concentration over a period of time, it can lead to severe physical damage and death.
Since CO is similar to the oxygen molecule O², the poisonous gas binds to the haemoglobin when absorbed through the respiratory tract and thus prevents the transport of oxygen through the blood. The affected person becomes unconscious and dies from lack of oxygen. At the same time, sick people, especially heart patients and unborn children, are more sensitive than healthy adults.
The Berlin Socio-Economic Panel (BSEP) found that foetal development is negatively affected. Newborns in regions with high CO exposure are almost 300 grams lighter than others. According to the latest findings, carbon monoxide poisoning (technically carbon monoxide intoxication) also increases the risk of developing Parkinson’s disease 8 to 9 times.
The first symptoms of CO poisoning include nausea, headaches, shortness of breath, dizziness and drowsiness. For further information Wikipedia offers a detailed article on carbon monoxide intoxication, which is based on the following table on CO concentration and symptoms i

If you detect symptoms of carbon monoxide poisoning, call the emergency doctor and immediately remove yourself from possible CO sources. If you suspect a fellow human being of carbon monoxide intoxication, make sure to protect yourself while you rescue him or her from the danger zone as quickly as possible. If the person is unconscious but still breathing, put them in a stable lateral position. In case of cardiac arrest, resuscitation must be performed. The emergency doctor can then take further steps.

Although the carbon monoxide content in the blood halves itself within about four hours, depending on the degree of poisoning, further treatment may be essential for survival. The affected person is usually intubated and ventilated with 100% oxygen. A hyperbaric oxygen treatment is also possible. Here the patient is ventilated with oxygen in a pressure chamber via tubes. In both cases the carbon monoxide is displaced from the bloodstream.

Is a CO detector useful for you?

In principle, a CO detector is useful if there are possible sources of carbon monoxide leakage.
Hospital data on cases of toxic effects of carbon monoxide on affected persons show that the documented case numbers in Germany have more than doubled between 2000 and 2015. To almost 3500, and the trend is rising. The number of unreported cases is probably much higher.
One or more CO-warners are useful if there are potential sources of carbon monoxide leakage in the household. For example, do you heat with a gas heater or have a fireplace in the living room? Do you cook with gas or do you have other appliances that run on gas or a combustion engine in general? Do you possibly live in an older house where there is a possibility that the exhaust air system or heating is no longer in optimal condition? Then we recommend that you install a carbon monoxide alarm for safety reasons.
Even if you like to smoke cigarettes or shisha in your apartment, a CO alarm is useful. As you have learned above, the CO concentration in the room can increase considerably due to the smoke.

What does a good carbon monoxide detector need?

Important are especially the durability, some features like display, memory or test function and quality seal.
The lifetime of the CO sensor is an important criterion. High quality carbon monoxide detectors have a life span of 7 to 10 years. In contrast, inferior sensors only last for about one year. This means that you have many times more work and cheap products of this kind are not economical or safety-related. Some manufacturers offer an additional guarantee of mostly 5 years.

You should make sure that the warning indicator is equipped with a permanently installed lithium battery. Then you do not need to worry about changing the batteries, as the lifetime is the same as that of the CO sensor. If you decide to use a detector with a replaceable 9 Volt battery, for example, it should have a “low bat” display.

Detectors with displays are preferred. You can then easily read the CO concentration or other information. To do this, the display must be large enough, easy to read and, above all, clearly visible. A display with backlighting is ideal.

A useful feature is the peak value and/or event memory function. On the display you can read, even after a longer absence, whether there was an increase in CO concentration, which peak value the concentration had and whether an A

In addition, your CO alarm should provide an opportunity to test it. Some detectors test themselves automatically, others offer a corresponding test button. In general, you should not just rely blindly on technology, but be able to test the CO sensor in some way. After all, it is your health and safety that is at stake.

Good carbon monoxide alarms do not simply sound the alarm at a certain CO level. Most have several alarm levels. When and after which time the alarm is triggered can vary. For a healthy adult the levels 50, 100 and 300 ppm are sufficient. In a child’s room, it is advisable to consider installing lower alarm levels with a shorter time delay, e.g. 30, 43, 80 and >150 ppm.

Also look out for quality seals! High-quality warning alarms are manufactured, tested and approved in accordance with national and international guidelines. If your CO detector has a TÜV, VdS and/or CE seal, this is always a sign of quality. In addition, your warning device should be certified according to EU guidelines.

Besides easy handling and installation of the CO meter, the volume of the CO alarm is of essential importance. The warning indicator is of little use if the alarm is so quiet that you cannot hear it. Most detectors are at 85 dB. But the alarm should not be quieter either.

A detailed manual in German and/or at least English is another important criterion. The warning indicator will not help you if you cannot (correctly) operate it, because the instructions are in Chinese or Russian. Unless you can read Mandarin or Cyrillic.

If you want to install several CO warning devices, make sure that they are wirelessly networkable and compatible. Especially if you live in a large building and the rooms are far apart. You should also consider the size of the room in which you want to install a CO-Warner. Not all warning devices are designed for all room sizes.

Carefully consider the requirements for the CO detector with regard to the size of the room, otherwise it may be ineffective!

What does a CO detector cost?

This question is not easy to answer. In principle, CO detectors are offered from 15 Euro up to the three-digit range. For quality products you have to calculate from 40 Euro.
In the forest of offers for carbon monoxide warning detectors there are products in every price range. Prices vary greatly depending on the area of application and equipment. No name products are available from around 15 euros. However, you should not make your choice of product primarily dependent on price. Above you have already learned what a good CO detector needs.
If you want to buy a CO detector based on these criteria, you can get a quality product for 30 Euros. If the detector is also to be wirelessly networkable, you will pay about 50 to 60 euros, depending on whether the wireless module is integrated or you retrofit it.
Good, free-standing or mobile warning detectors are also available from 30 euros. Professional devices, on the other hand, range between 150 and 180 euros. Carbon monoxide smoke and/or heat detectors are cheaper as fire detectors, but less useful than pure CO detectors because of the problems mentioned above. Gas detectors, on the other hand, cost around 70 euros, but the problems mentioned are similar to those with fire detectors.
These carbon monoxide detectors cover the above mentioned criteria to a minimum. Of course there are also much more expensive branded products that go beyond this minimum level.
The additional module for the hearing impaired is available for about 130 Euros. Depending on the manufacturer, the price varies up to 180 Euros, but the functions differ only slightly.
We have summarized everything in the table below:

Where can you buy a CO detector?

Naturally on the Internet on the well-known buyer portals and dealer sites for security technology. In addition, most DIY stores and dealers for security technology carry CO detectors and additional equipment.
The first place to go when you want to buy a CO warning device is of course the Internet. You can buy anything there. You will be inundated with offers on the well-known buyer portals. But security technology dealers also offer the various types of CO detectors on their websites.
You can also find portable CO detectors on the websites of dealers of fire or rescue equipment. Here you can usually find more detailed information about carbon monoxide and CO detectors, as well as often very detailed product descriptions.
Of course, you can also go to a DIY store or visit a safety equipment dealer in person. Although this requires a little more time and effort, you can get first-hand advice there. Since the purchase of a CO detector should not be an impulse purchase and you should inform yourself properly about the product, this option may be better. However, you will have to weigh up the advantages and disadvantages of Internet information or purchase and personal consultation yourself.
Here is a small selection:

fire department

How many CO detectors should you buy?

Every room containing a potential source of CO leakage should be secured.
For example, if you have a gas heater in the basement, a gas stove in the kitchen and a gas heating mushroom in the conservatory, you should definitely equip these rooms with CO alarms. Wirelessly networked warning devices are recommended, as all detectors sound the alarm as soon as one detector measures a dangerous CO concentration. Basically, you should consider which sources of CO gas are available in your home and secure these rooms with carbon monoxide alarms.
It may also make sense to secure a room with an alarm that does not directly contain a carbon monoxide source. Since this toxic gas rises very slowly, it can happen that it “spills” into a room unnoticed. So before you do this, think about which rooms you need a carbon monoxide alarm in.

What standards should your CO detector meet and what certifications are available?

The EU standard EN 50291 should be fulfilled in any case. A CE marking, a TÜV and VdS seal are further quality features.
The European standard EN 50291 generally regulates the requirements of electrical CO measuring instruments for operation in residential buildings in the areas of construction, test methods and operating behaviour. If you would like to get more detailed information about this standard, you can do so on the website of the German Association of Electronics (VDE). However, the text of the standard costs…
The CE marking indicates that the product complies with the product-specific applicable European directives. Although this seal is not a test seal but an administrative mark, it nevertheless indicates that European directives are complied with.
You certainly know the TÜV seal. The TÜV tests technical products neutrally, expertly and independently and certifies products that meet the high requirements. The seal “TÜV-tested” is at least colloquially a seal of quality, but is relatively rare for CO detectors.
A certification by the VdS (Vertrauen durch Sicherheit) Schadenverhütung (Trust through security) Loss prevention products of the civil security market as well as security and safety companies. A VdS seal indicates that the product-specific requirements of the CO detector exceed those of the European standard.

Decision: What types of CO detectors are there and which one is right for you?

Basically one can distinguish the following types of carbon monoxide detectors:

  • Standard-CO-Melder
  • Radio CO detector
  • CO detector for the hearing impaired
  • CO smoke and/or heat detector combinations
  • Gas detector
  • Portable/mobile CO detectors

The detector types have different functions or areas of application and thus individual advantages and disadvantages. In addition, there are combinations of the different detector types.

Depending on how big your home is, in which room you want to install a carbon monoxide alarm or from which dangers you want to protect yourself additionally, different functions are useful. Maybe you also need a CO alarm for your caravan or want to use it flexibly in different places. The following section will help you determine which type of carbon monoxide detector is right for your needs.

To this end, we present the types of CO detectors listed above and clearly explain their respective advantages and disadvantages.

What are the advantages and disadvantages of standard CO detectors?

Standard CO detectors or stand-alone detectors can do exactly one thing: sound the alarm as soon as the concentration of carbon monoxide in the room exceeds a certain level. But there are also models that are additionally equipped with some very useful functions.

Since even a low, not immediately lethal concentration of CO gas can lead to physical damage over a certain period of time, the acoustic alarm of most warning detectors, e.g. with a low CO concentration, only sets in after 60 – 90 minutes, with a high concentration sc

There are also CO detectors with LCD displays or LED control lamps for better monitoring of, for example, carbon monoxide concentrations. The acoustic warning signal and features are of course also present in the other CO detector types and are only mentioned here as an advantage over not using CO detectors.


Acoustic warning signal for excessive CO load
Various useful features

Comparatively inexpensive


May not be audible in large houses and halls
Works “only” on carbon monoxide
Mostly fixed to the wall/ceiling

Features as mentioned above, (automatic) function check or memory functions naturally have an effect on the price. As always, the manufacturer and the quality of the device also play a role.

If you live in a large house or need CO detectors for (warehouse, production, etc.) halls, it is possible that the alarm may be overheard by the distance or locked doors despite its volume. In this case you should use wireless CO detectors.

We see the fact that a CO detector “only” reports CO as a disadvantage here only for the reason that combination devices with additional (e.g. optical) sensors can also detect smoke and sound the alarm.

A high CO concentration does not necessarily mean a fire. That’s why you should use a smoke detector as a fire alarm, which is usually cheaper.

What can wireless CO detectors do and what are their advantages and disadvantages?

CO radio warning detectors can be coupled together via an integrated or additionally available radio module. Via this module, the CO detectors can also communicate with other additional devices to form a complete home system.

The problem of standard CO detectors in large houses or halls can be solved by radio networking. The warning detectors are linked together via the radio module. If the CO concentration rises in a room with a CO detector, the CO detector sends a signal to all devices connected to it, which then also trigger an alarm. In this way, an increase in carbon monoxide gas does not go unnoticed even if the alarm is triggered in a remote cellar or similar.


No alarm goes unnoticed (even in large buildings)
Several CO detectors, additional devices and other detectors can be wirelessly networked
Usually no separate power supply of the radio module necessary
Mostly simple retrofitting of the radio module possible


Works “only” on carbon monoxide
Mostly fixed to the wall/ceiling
Relatively high price for CO detector incl. radio module or retrofit module

It is therefore not only possible to couple several CO warning detectors together, but also to integrate smoke detectors or detectors for other harmful gases into the system. This makes the wirelessly networked CO detector also interesting for industry.

Many companies have installed such systems in their warehouses and production halls. For private use, for example, additional devices such as a vibration or optical signal for the hearing impaired can be embedded in the system.

Many manufacturers state that the separate radio module can be easily retrofitted with just a few simple steps. In addition, the module is also powered by the power supply of the carbon monoxide detector. This means no additional battery waste.

What are the advantages and disadvantages of CO detectors for hearing impaired people?

This type of warning detector is actually not a CO or smoke detector per se, but an additional device that can be embedded in the warning system via radio. However, since, depending on the source, 15 – 16 million people in Germany are affected by hearing loss, we think it makes sense to present you with this solution.

Radio-networked warning alarms are a prerequisite for the hearing impaired alarm. It does not matter whether CO, gas or smoke detectors or combinations of detectors are connected in the network.

At least the leading manufacturers guarantee a smooth signal exchange between the various radio detectors and between them and the additional device for the hearing impaired. Nevertheless, for safety’s sake, you should make sure that you purchase the detector components from the same manufacturer.

As soon as a CO detector registers an increasing CO concentration, the warning detector for the hearing impaired alerts you visually via an intense strobe light. In addition, a vibration cushion is connected which is placed in the pillow. This ensures that you are awakened in case of danger.


Safe alarm system for hearing impaired people
Mostly emergency battery/accumulator available (power failure)
Compatible with different and multiple detector types and radio networkable
Freestanding (Within the cable length)


Wireless networking sometimes not easy
Relatively high price (in addition to the actual warning alarms)

The warning detector is connected to the socket and can be placed flexibly in the room thanks to its relatively long connecting cables (connection of device socket and device vibration pad) of 3 – 5 metres.

Most manufacturers have provided the device with a rechargeable battery or a 9-volt battery in addition to the power connection. This emergency power supply ensures that the alarm will go off reliably even in the event of a power failure.

Even though the alarm for the hearing impaired is compatible with various smoke, gas and CO sensors, problems can still arise during the first wireless connection. For example, the website reports initial difficulties in establishing the first radio connection with other components.

What can CO smoke and/or heat detector combinations do and what are their advantages and disadvantages?

If, in addition to carbon monoxide, smoke and fire are to be warned, a combination detector with different sensors supposedly saves the installation of several detectors.

Such multi-sensor detectors reduce the risk of false alarms by measuring carbon monoxide concentration in the room, smoke density and/or temperature rise. However, only in the event of a fire alarm.

If you have considered not only protecting yourself from carbon monoxide poisoning but also from fires and not plastering every room with warning alarms, a combination device might make sense. However, there are some things to consider here.

In principle, a combination device also measures the carbon monoxide concentration and sounds an alarm if a limit value is exceeded. But now you have to decide whether you want to use the warning detector more as a CO detector or smoke detector.

This is because smoke moves quickly with the warm air of a fire towards the ceiling and carbon monoxide spreads very slowly because it has almost the same density as the air in the room. If the carbon monoxide reaches the ceiling, the whole room is usually already flooded. Even with a CO-thermal detector combination you are faced with this problem.

Many products of this CO detector type are offered as “smoke and CO detectors” or “combined CO detectors”. However, a closer look at the description will usually reveal the actual area of application for the carbon monoxide sensor: Slowly spreading fires or sulphur fires have a relatively low smoke emission, but produce carbon monoxide gas.

This means that the warning indicator can sound the alarm in these cases as well. Multi-sensor detectors are therefore often already offered as fire detectors, such as the 3-sensor combination from Bosch.


The risk of false alarms is reduced
Detects any kind of fire
Inexpensive medium quality products available


Decision problem in the area of application
Very high price for high quality products
As a pure CO detector only useful with very low ceilings

As mentioned above, a combination device CAN be used as a pure CO warning device if it is mounted accordingly. The website www.testberichte.dekommt also concludes that such a combination device as a CO detector makes little sense from a practical point of view. It can only reliably warn against one or the other.

However, such a device is useful in small rooms with a very low ceiling, e.g. in a caravan or inside a boat. Here the CO concentration can be measured better.

However, we would like to point out that you will have to deal intensively with the product before purchasing a combination device if you want to use it as a pure CO detector. If in doubt, we advise you to use two separate warning detectors.

What can gas detectors do and what are their advantages and disadvantages?

Gas detectors measure the concentration of various toxic gases and sound an alarm as soon as a limit value is exceeded. Gas detectors are offered which detect methane and ethane (natural gas), propane and butane (liquefied gas) or carbon monoxide and warn against too high concentrations. Combined devices are also available. This leads to a known problem.

As you can probably imagine, carbon monoxide, natural gas and liquid gas have different densities. Therefore, it is necessary to install the gas detector either on the wall, the ceiling or near the floor. A combination gas detector that detects carbon monoxide and liquid gas or carbon monoxide and natural gas with the respective sensors is therefore of little use.


Detects different gases
Mostly very simple assembly


Decision problem in the area of application
Compared to the pure CO detector, relatively high power consumption
As a pure CO detector only useful with very low ceilings

Gas detectors usually have to be connected to a socket. On the one hand, this simplifies installation, on the other hand, a gas detector requires more energy compared to a conventional CO or smoke detector.

This is due to the fact that a wire inside the warning indicator is made to glow by a continuous current supply. If a gas comes into contact with the glowing wire, heat is generated by the combustion. If there is enough heat, the gas detector sounds the alarm.

As with the CO smoke and/or heat detector combinations, we encounter the problem with the combination gas detector that different installation locations make sense for different gases. So it does not reliably warn you of different gases in parallel.

A gas alarm is useful in small rooms with a very low ceiling, e.g. in a motor home or inside a boat. However, we would like to point out once again that before you purchase a combination device, you must familiarise yourself intensively with the product if you want to use it as a pure CO detector. If in doubt, we advise you to use separate warning devices.

What are the advantages and disadvantages of a portable/mobile CO alarm?

Portable CO detectors are often carried by fire and rescue services during operations. But portable and free-standing CO detectors can also be useful in private use.

Small, portable carbon monoxide detectors are used by fire and rescue services to assess the safety of operations. These hand-held devices are often very functional and are therefore less suitable for use in the home. However, there are freestanding and portable CO detectors in modern or simple designs that are indistinguishable from other warning detectors.


Functional, modern or simple design available
Flexible use at different locations
Combination of different sensors makes sense


Mostly no radio networking possible

A CO alarm that can be used flexibly in different rooms or taken with you on holiday, car or caravan sounds sensible. In our opinion it is. In this case, the combination of a CO sensor with sensors for other toxic gases, smoke or heat would also make sense.

Depending on the area of application, you can place the warning detector in the optimal location. But for this you need to know the behaviour of the respective gas. Again, you should not use a combination device for different gases and/or fires at the same time.

The only shortcoming of the portable or free-standing carbon monoxide warning detectors is the usually missing ability to be networked with other warning detectors and devices via radio.

Purchase criteria: You can use these factors to compare and evaluate CO detectors

The following article introduces the factors you can use to compare and evaluate carbon monoxide detectors. This should help you decide whether a particular device is suitable for you or not.

In summary:

  • Product weight
  • Product dimensions
  • Room coverage
  • Operating temperature
  • Power supply
  • Sensor lifetime
  • LCD display
  • Battery level indicator
  • Control LED
  • Audible and visual alarm
  • Alarm levels
  • Alarm volume
  • Test function
  • Memory function
  • Certification
  • Guarantees
  • Fields of application
  • Wall mounting / stand mounting
  • Instruction D/E

In the following paragraphs you can read about the individual criteria and how you can classify them.

Product weight

This criterion is particularly relevant for mobile CO detectors. The lighter a warning detector is, the more handy and practical it is when used flexibly.

For CO alarms that you mount on the wall, this criterion is not really important. Your wall should be able to detect any type of CO detector

But if you tend to have a mobile CO alarm, for example because you want to take it with you on holiday, it is of course more practical if it is as light as possible. Weight is even more important for CO detectors that you want to carry with you at all times. This is the case, for example, with fire and rescue services.

Product dimensions

The “size” of the warning device is not only important for mobile devices. The larger a wall-mounted CO detector is, the more it attracts attention.

The larger the CO-Warner is, the less practical it is. This applies mainly to mobile CO detectors. However, freestanding detectors also take up unnecessary space. So why buy a large warning detector when you can have the same functions in a more compact form?

A CO alarm that you mount on the wall should be clearly visible and the display should be large enough and easy to read. However, its size should not attract attention and it should be discreet.

With today’s technical progress, you can orient yourself by the following guiding principle:

As small as possible but as large as necessary.

Room coverage

The room size should not exceed the detection range of the carbon monoxide sensor. Unfortunately, manufacturers do not always provide this information.

Especially for large rooms it is important to know the maximum detection range of a CO sensor. If the room size is above the specified maximum value, the alarm may not be triggered.

Unfortunately only a few manufacturers provide this information. The coverage areas researched by us vary from 20 – 60 m². If you are not sure and want to equip a larger room with a CO detector, an e-mail to the manufacturer can help or you can go to the specialist dealer and ask a competent employee personally on site.

Operating temperature

You want to install a CO alarm in the basement? Even though almost all alarms are operational from 0 °C, it may be useful to consider a warning device with a wider operating temperature range.

In cellars without heating it can get quite cold in winter. Similarly, smaller rooms can heat up considerably if they are exposed to strong sunlight during the day in summer. This can lead to the CO sensor not functioning properly and the alarm not being triggered. Or it can lead to false alarms.

The lowest range in which CO sensors function perfectly according to the manufacturer’s specifications is between 0 and 40 °C. Certain warning indicators have a wider range of -10 to a maximum of 50 °C. If you are unsure, first determine the room temperature using a thermometer.

Power supply

Not only for the sake of the environment, permanently installed lithium batteries are useful. Even if you are reminded to change the batteries via an LED or a display, this can be overlooked.

Many CO detectors are powered by one to three AA batteries or a 9 volt block battery. When the battery life is coming to an end, you will be advised of this on most models. Then new batteries must be inserted and the old ones disposed of.

The danger here is to simply overlook this, despite the LED and/or display. After some time, one often does not actively pay attention to smaller changes…

The newer models of the leading manufacturers are usually equipped with a permanently installed lithium battery. The service life corresponds to that of the CO sensor. Therefore you do not have to worry about the batteries. Furthermore, one lithium battery and several AA or block batteries make only a slight difference in terms of cost.

Another possibility is to supply power via the connection to the socket. This is the case with many gas detectors, as they require a comparatively large amount of electricity.

Sensor lifetime

The lifetime (up to 10 years) of the CO sensor is one of the most important criteria. From an economic point of view alone, cheap products with a short service life (e.g. 1 year) make no sense. It is more worthwhile to invest once in a quality product with a long service life.

Many no-name products may seem like bargains at first, but often have a very low life expectancy. In most cases, this life expectancy is between one and three years. Then the CO sensor breaks down, the warning indicator no longer recognizes the gas and must be replaced.

Current products from leading manufacturers already achieve a sensor service life of up to 10 years. These are a bit more expensive to buy, but you will have a quality product and therefore a more productive device in this area.

LCD display

Via a display you can easily use different functions of the CO alarm, depending on the supplier and model. Display the ppm value or temperature, check the battery level, read the memory, etc.

Nowadays there is just about every product with a display, even toothbrushes. But with your CO detector, a display like that actually makes sense. Additional features that many alarms bring with them can usually be controlled very easily with a display. Important features are presented below as additional criteria.

Reading the ppm value or reading the peak value memory is not possible without display. So a display should have your CO alarm in any case. A useful gimmick is a temporary backlight to guarantee the readability of the display.

Battery level indicator

A battery level indicator is important! Your CO detector should in any case alert you in some way to the fact that the battery is running low.

Many warning indicators alert you to low battery levels via a red or yellow LED. This LED flashes or lights up continuously over a certain period of time. This is especially important for battery-powered devices, where you need to change batteries more often.

If the CO alarm has a display, on some models the battery level is shown continuously on it. So you can also see in advance how long the AA or lithium battery will last. An additional flashing LED for low battery level is also useful here. This will remind you even if you don’t always check the display actively.

Control LED

To check the operability, an LED should inform you of this. Either permanently or at the latest in case of a malfunction.

Not all CO warning devices show you via a green flashing or permanently lit LED that there is nothing wrong with your carbon monoxide detector. On the one hand this would be a useful feature, on the other hand such a flashing light can be extremely annoying, especially in the bedroom.

For bedrooms there is another solution. You can perform a manual test on many CO alarms, whereupon an LED will inform you whether your device is working properly. Other alarms are equipped with a self-test function. If this test shows that any function is not working properly, this is automatically signalled by a flashing red or permanently lit LED. Some detectors also sound an alarm.

Audible and visual alarm

Visual signals are of particular importance for hearing impaired people. However, you have to decide whether a flashing LED is enough or whether you need an additional module for the hearing impaired. This is also about alerting in case of malfunctions.

In addition to the acoustic alarm, some warning indicators also give you a visual signal if there is a CO danger or that something is wrong with your device. If a CO alarm is triggered, a visual alarm is useful for hearing impaired people. Whether a flashing LED is sufficient is another question. For the bedroom, we recommend that you use an additional module for the hearing impaired. This will wake you up in any case.

However, it is also possible that only short regular alarm tones are emitted in the event of a malfunction. If this is less easy for a hearing impaired person to detect, a visual signal can alert that person to the malfunction and appropriate action can be taken. Since the danger is not acute, an additional visual alarm can be an alternative to the expensive additional module.

Alarm levels

For carbon monoxide alarms, there are legal requirements as to the concentrations above which the alarm must be triggered within a certain time. For small children, for example, it can be useful if the alarm is triggered earlier.

The legal requirements according to EU certification EN 50291 state that the CO-Warner must alert you at carbon monoxide concentrations of 50, 100 and 300 ppm within a certain period of time.

You can find the exact data in the table in the section Trivia – How does a CO detector work?

However, small children, pregnant women and people with heart disease are more sensitive to carbon monoxide and even a low concentration can cause damage. For rooms of affected persons it is then advisable to pay attention to the alarm levels when buying a CO alarm. There are devices on the market that already sound at lower concentrations than the legal minimum requirements.

Alarm volume

The legal minimum volume of a CO warning indicator is 85 dB. So make sure that your CO detector does not fall below this value! Otherwise it is probably not approved in Europe.

The volume of CO detectors is usually indicated in dB at distance. For example, an indication of 85 dB at one meter means that the alarm has a volume of 85 dB when you are standing one meter away from it. This is about the average volume of a petrol lawnmower.

A value below this volume is not permitted by law. Therefore you should also pay attention to this product information.

Some, louder CO alarms still reach 85 dB even at three metres. But much louder alarms are rather the exception.

Test function

You should be able to test your CO warning device. How else would you know if it works?

Most CO detectors are equipped with such a function. No matter if you have to test manually via a test button or if your warning detector has a self-test function. This ensures that all functions work properly. If something does not work properly, you will be alerted by a visual and/or acoustic alarm.

If your CO alarm is not equipped with one of the two features, the only option is to purchase a test gas. Because you should definitely test your warning device. Otherwise it may be useless.

Memory function

This function allows you to see whether an increased CO concentration was recorded or an alarm was triggered during your absence.

If you should be absent for a certain time, for example on holiday, you can find out various things using the memory function. Most warning devices will tell you if an alarm has been triggered during your absence. In addition, some CO detectors also record smaller increases in CO concentration and then display these via the peak value display.

Even a small increase in the CO concentration can be an indication of a leak or CO source. With a peak value storage function, you will be notified of this possibility on your return and can get to the bottom of it.

The storage duration varies greatly across the models.


On the basis of the certificates you can see whether a CO detector is approved in Europe and meets the national requirements. Your CO alarm should at least comply with European standard 50291 of 2010.

EN 50291-1:2010 are the European minimum requirements for a carbon monoxide alarm detector for domestic use. Your warning device should definitely comply with this standard.

Note, however, that this standard only applies to private households. If you want to install your CO alarm in a caravan, motorhome or boat, the warning device must also comply with the standard EN 50291-2:2010. If both partial standards are met, the manufacturer usually simply states “EN 50291 certified”.

You can read the relevant standards and certifications in the section Advisor – Which standards should your CO detector meet and which certifications are available?

If you choose a CO smoke and/or heat detector combination or a gas detector, please note that your detector must comply with other standards. If you want to be warned against other gases, temperature and smoke besides carbon monoxide, there are special standards for this.


A manufacturer’s warranty, whether over 3 years or the entire service life, is a plus point.

The leading manufacturers actually always give a guarantee. Often over 3 – 5 years, with the newer models sometimes over the entire life of the CO sensor.

With it you get a free repair or a replacement device, should your warning device break down.

Fields of application

Where you can use the CO alarm depends on the EU certification. Besides warning devices, exclusively for household use, some CO-alarms can also be used in caravans, motor homes and boats.

This criterion is intended to show you where you can use your carbon monoxide detector if you are not familiar with the relevant EU standards and certifications. Although the areas of application depend on these standards, it is quite cumbersome to find out about each standard.

Not all carbon monoxide detectors can be used in all areas!

Trivia: Facts worth knowing about CO detectors

How does a CO detector work?

The carbon monoxide detector has an electrochemical sensor that measures the concentration of carbon monoxide gas in the room air.

The electrochemical sensor cell is based on tin dioxide (SnO²). If this substance comes into contact with carbon monoxide, the conductivity changes through a reaction. Even the smallest change in conductivity and the associated change in resistance is analysed and evaluated by the CO detector. In the case of low CO concentrations, the warning device calculates the time period in which it becomes dangerous for people and triggers the alarm beforehand.

There are legal minimum requirements for the time until the alarm is triggered depending on the CO concentration:

The alarm levels can usually be found in the product details. Many carbon monoxide detectors also have a pre-alarm, which is activated at lower concentrations. Usually via an optical signal on display or via an LED.

How and where exactly do you install your CO detector?

You can find the “how?” in the enclosed assembly instructions. CO detectors should be installed in the middle wall area in rooms with CO sources as well as in bedrooms and living areas.

Above you have already learned which sources there can be for a carbon monoxide leakage. CO detectors should be installed in rooms with such sources, in bedrooms and living rooms as well as in fuel stores. The alarm must be audible everywhere, so think about a wirelessly networked carbon monoxide alarm. Especially if you live in a larger building.

The warning indicator is mounted in the middle to upper wall area at a height of approx. 1.50 to 2.00 m. The display must be clearly visible. You should keep a distance of at least two metres to the CO sources, otherwise there is a risk of a false alarm. It is even more important that you do not install the warning detector near windows, doors, extractor hoods or similar.

Incoming fresh air and the draft in general can strongly falsify the measured values. In the worst case, the CO detector will not even trigger the alarm. Other circumstances that can lead to incorrect measurements are strong climatic fluctuations and high humidity such as in showers or bathrooms. If you are unsure, ask a competent dealer for safety

If you don’t happen to opt for the mobile version, CO detectors are usually fixed to the wall with two screws and plugs. The size of the screws and the depth of the drill holes vary. Fastening with glue, magnets or the like is also possible. For more details, please refer to the enclosed operating and installation instructions.

How do you maintain and test your CO detector?

For battery-powered CO detectors, maintenance simply consists of changing the batteries and a test. Many CO detectors have a self-check function or at least a test button. However, only a CO detector test device is really reliable.

From time to time you should maintain or test your CO detector. With battery-powered warning detectors, you do this as soon as the batteries need to be changed. This is not necessary for detectors with a lithium battery, as their service life is the same as that of the CO alarm.

The self-check function of some CO warning devices tests itself and notifies you of malfunctions via the display, an LED or a separate alarm. For devices with a test button, you must perform the test manually.

To be on the safe side, you can also get a CO detector tester. With this you can test if the CO sensor really reacts when it gets in contact with carbon monoxide gas and sounds the alarm.

What to do on a carbon monoxide alarm?

Don’t panic! Open the windows and leave the house quickly with your family or other residents. Then dial the emergency call.

If the CO alarm is triggered you should react quickly: open the windows. Of course you should not run around the house in panic and open every window. This is more about getting some fresh air into the room you are in.

Then you and your family leave the house and inform the other residents if they have not heard the alarm. But only as long as you do not endanger yourself.

Then dial 112 for the emergency call and wait until the rescue service or fire brigade arrives. You must then inform them of your suspicion of carbon monoxide poisoning.

It is important that you do not enter the rooms again until they have been released. Even if the carbon monoxide problem is solved and it seems safe again, it is of utmost importance that the CO sources are found and appropriate repairs are made!

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