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 Updated: 8 Jan 2016



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The exchangeable sensor X-CHANGE turns the recalibration into a home game:

  • Delivery of recalibrated sensor cartridges

  • Easy exchange, no specialized company needs to come to you

  • Available for every gas type

  • At guaranteed exchange prices

  • Increased reliability (SIL2-software)

  • Important time and cost savings

The X-Change support guarantees a price based on the consumption of the sensor capacitance.

For each uncalibrated sensor returned to AP, you will receive a credit for the unused capacity of the sensor.

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Legal and safety requirements
The devices are manufactured according to the regulations and various directives such as
EN 50545, etc.

Products delivered by AP meet and even exceed the new European Standard EN 50545.

The safety features check the connected warning devices on functionality and open circuit day and night (Level SIL2 according to EN 50271).


Quick and easy replacement of sensor

  1. Open the housing with a screwdriver.

  2. Disconnect the sensor cable and unscrew the disused sensor head.

  3. Exchange the sensor cartridge (3) and connect the cable of the new sensor head to the PCB.

  4. Close cover of the housing with the screws (1). The recalibrated sensor is ready for use at once.



One of the most common causes of fatal accidents due to gas is when the oxygen concentration drops.

It may, for instance occur when another gas displaces the oxygen.

Man's own warning signals for lack of oxygen are not reliable.

The symptoms are almost unnoticeable and the victim does not react until it's too late.

Gagging symptoms include shortness of breath, increased breathing rate, numbed responsiveness and impaired muscle coordination.

Oxygen concentration in the air is normally 20.9%.

The table below shows what happens to the oxygen concentration when another gas dilutes the air:

Concentration of diluted gas

Oxygen concentration


0.5 20.8
1 20.7
5 19.9
10 19 (flashlight)
15 18.2
20 17.4 (gas alarm sign)
25 16.7

Symptoms of hypoxia are already shown when the concentration falls below 17% O2.

If the O2 concentration drops another 2-3% this indicates mortal danger.

Alarm limits for decreasing concentration of gas is set to 18-19%.

Other reasons why oxygen levels can fall are among others:

  • Combustion of somthing which consumes oxygen

  • Corrosion of something that reduces the oxygen concentration

  • Oxygen consumption due to breathing in dense areas.

Problems usually arise in confined spaces such as tanks, tunnels, etc.

Oil- and gas industry
The normally closed spaces like tanks, containers, pontoons, etc.. corrosion may have contributed to making oxygen levels drop to low values.

A worker entering such an area may die immediately.
Therefore, it is important to first check the oxygen concentration in the compartment.

In some cases, other gases may be present, both toxic and explosive. Therefore it may be necessaru to use a portable instrument that measures several gases at the same time.


Before stepping into, for example, a tank you should check the oxygen concentration in the tank with a portable gas detector.


In tunnels, such as sewers and other underground facilities the oxygen concentration may drop for for various reasons.

In addition, other, both explosive and toxic gases may have been formed as a result of biological reactions.

For example, CH4 (methane), H2S (hydrogen sulfide), CO (carbon monoxide).

An combustion engine underground may consume the oxygen and leave carbon monoxide behind.

Leakage of different gases that are lighter or heavier than air, may lead to accumulation in different cavities.

When someone enters into such a cavity without first checking gas concentrations with an instrument it may lead to immediate death.



Sensor placement for monitoring oxygen
In cases where you want to monitor oxygen concentration in a room, it is important to bear in mind which gas that could displace the oxygen.

Examples of gases that can displace oxygen, thereby causing suffocation are the inert gases, such as Nitrogen (N), argon, helium, carbon dioxide, used in various industrial processes, hospitals, etc.

Important to mention here is that the fact that the carbon dioxide in addition to displacing the oxygen is also toxic itself.

If there is leakage of, for example, krypton, which has a higher density than air and will sink, the oxygen detector should be placed low.
If a gas with lower density than air, such as helium, should leak, the oxygen sensor should be placed high.

If the oxygen in a room risks being consumed by any form of combustion, the oxygen concentration will be reduced across the room which means that the sensor placement here is not as critical as in the above examples.


High concentrations of oxygen
If the oxygen concentration in the air increases, the risk of fire dramatically increases. All combustible products will be much more flammable.

Alarm limit is set at 23% O2.
Inhalation of high oxygen concentrations over time can be harmful.

How many detectors are needed in a stationary system?

This must be decided from case to case depending on the local area that you want to monitor, but as a rule of thumb you can use the following:

One detector per 100m2, with additional detectors at locations where leakage is likely occur.



O2025, IP65, Standard - Wall design





Modbus Manual Manual



DUCT - IP65, Duct design





  CE Address list

Protection class


O2025 DISP, IP65, Oxygen detector with display



Gas Central O2SP for 1-2 sensors (1 built-in) with
relay outputs for 4 alarm levels, internal
buzzer, operator panel and display








Warning lights for oxygen detectors











Gas alarm plate for oxygen detector


Warning Siren for oxygen sensors


Combined warning siren and flash light for
oxygen sensors


ATEX Gas detectors are available for 2 explosion classes as follows:

Zone 1 is available with or without display.

Gas detectors for ATEX Zone 1 are located in a flameproof enclosure, EEx d

The shell is such that ignition and combustion within the shell of a potential explosive gas mixture is not propagated to the explosive mixture outside the enclosure and the enclosure can thus endure the resulting explosion pressure without damage.



In Zone 1, one can expect an explosive atmosphere to occur during normal operation but the presence of it is relatively short.

The equipment shall not be a source of ignition in normal operation or when an error occurs.

Gas detectors for ATEX Zone 2 are of the design Non-sparking EEx nA

EEx nA is a non-sparking piece equipment.


In Zone 2, you need not count with an explosive atmosphere to occur during normal operation, and if it should occur, which is probably rare it is of short duration.

The equipment shall not be a source of ignition during normal operation.









Address list

EEx-d ATEX Protection Class


EEx-n ATEX Protection Class



E-mail: ewert@automatikprodukter.se     

Phone: +46(0)31-287202

Mobile: +46(0)708885298



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