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Help – Toxic gas detection, flammable gas detection, flame detection and associated controllers

How to use
The Drager electronic gas list is designed to help you easily find the correct Drager product to assist you with toxic gas detection, flammable gas detection or flame detection.

By entering either the substance name, the CAS number or the Sum formula then this simple to use program will direct you to the correct product to use as well as providing you with suitable measuring ranges. If a substance is not found this does not necessarily mean that Drager cannot measure this, our comprehensive R&D facility is researching and testing new substances all the time and it may be the case that the gas list does not currently reflect these developments – please contact us if you cannot find a solution to your substance detection problem.

Automatic updates
If you are using this facility via a USB we do periodically release updates. When an update is available you will be prompted via a banner at the top of the screen when you start the program or insert the USB (providing they have a connection to the internet). Clicking on this link will download the latest version and update the database. You will note that the Version No. on the bottom left hand of your screen will change. If you are not sure if you have the most up to date version or if your update has not worked please visit

Internet Access
Some links/glossary terms require access to the internet, these links were correct at time of publication and we have endeavoured to ensure that they are as free of viruses/malware as we are able.

Search Indexes

This list of gases consists of three search indexes and the main part. The search indexes are suitable to find the substance in question by having only its name (including short name or technical abbreviation), its sum formula, or its CAS-number.

Using the search indexes you will obtain the substance’s associated number to look for in the list of gases.

If the substance is not listed, this does not necessarily mean that this substance is not detectable by Polytron equipment.

Search Index for CAS-Number

The CAS-number is a worldwide used code to identify a chemical substance unambiguously. This number is issued by the Chemical Abstracts Service and is the easiest way to characterize a chemical substance. Knowing the CAS-No. means to be able to get comprehensive information and links from internet and search engines.

The considered substance is unambiguously specified by the CAS-No.

Search Index for Name / Abbreviation

When sorting alphabetically the chemical prefixes such as n-, i-, sec-, tert-, N-, N.N-, or numbers were omitted.

Please proceed correspondingly when looking for a substance.

When searching 1.2-Dichloroethane look for Dichloroethane, find tert-Butanol under Butanol and Methyltert butylether under Methylbutylether.

This search index also lists short names or technical abbreviations. However these names may be ambiguous from chemical aspects (e.g. Dimethyl ether and Dimethoxy ethane usually both are short-named as “DME”).

Furthermore refrigerants were considered. The code basically is preceded by “R” meaning refrigerant although in other countries characters such as “F”, “FCK”, “HFA” or names such as “Freon”, “Frigen” and “Propellant” etc. are used. So, if you look for e.g. Freon 134a please search for R 134a.

Search Index for Sum formula

For every chemical formula – normally given as a semi-structure formula – a sum formula exists. A sum formula is formed according to the Hill-system: Within each sum formula the element symbol C (for Carbon) is on the first place, the element symbol H (for Hydrogen) on the second, followed by all other element symbols in alphabetical order. For every element symbol the order is given with increasing number of atoms of the corresponding molecule. So it seems a little bit strange having a sum formula of e.g. ammonia H3N, of sulphur dioxide O2S and of hydrogen cyanide CHN.

Having the chemical formula of a substance, the individual element symbols have to be summarized and sorted accordingly. With the sum formula obtained this way you can go into the search index for sum formulas to get the substance’s associated number.

Example: CH3COOH

Sum formula is C2H4O2. This is the sum formula of acetic acid. But you can verify that this is also the sum formula of Methyl formate (HCOOCH3).


Sum formulas may be ambiguous!

The Gas List

This list is the real list of gases. For each substance there are at least three lines. Besides the column of the current number the gas list comprises 17 columns which are explained in the following:

Column 1: Substance / Chemical Formula

The main name covers two columns in the first line. The 2nd line shows the CAS-No., and the 3rd line shows the chemical formula.

Column 2: Shortn. and S-formula

If there is a technical abbreviation known it is listed in this column 2nd line. The sum formula is printed in the 3rd line.

Column 3: Synonyms

If further names are known the most usual ones are listed here.

Column 4: Molw. g/mol

In the first line the molecular weight (mol weight) M is listed. The mol weight is used in many calculations, e.g. you can calculate the relative density of a gas or vapour by dividing value M by 28.96. If the result is less than 1 the gas is lighter than air. In most cases the result will be greater than 1 – so it is heavier than air. In case of vapours, however, the maximum vapour pressure (the maximum concentration at a given temperature) in an air/vapour mixture has to be regarded (see vapour pressure column 7): Vapours can never exist in a 100 %v/v-concentration!

Below the mol weight the value of the relative density compared to air is listed. It is marked by a subsequent “r” (for relative).

Example: n-Butanol: 2.56 r

Vapours of n-Butanol are 2.56 times heavier than air.

By using the mol weight M you can convert concentrations given in %v/v (= % by vol.) or ppm to obtain g/m3 or mg/m3.

Using the mol weight M you can also calculate the density of a gas in kg/m3 (at 20 °C and 1013 hPa) by simply multiplying with a factor of 0.04179:

Example: The mol weight of Propane is 44.1 g/mol, so the density of Propane is: ρ = 0.04179 . 44.1 = 1.843 kg/m3

If density ρ and mol weight M are known you are able to calculate the amount of liquid to be evaporated in a given volume to obtain a defined vapour concentration. However, it is very important that this liquid is evaporated completely. This requires a sufficiently high vapour pressure.

Use the “calibration chamber formula”: To obtain a vapour concentration c in a volume of 3 litres at 20 °C and 1013 mbar you have to insert the following amount F (in microlitres) of the liquid:

Example: Ethyl acetate, M = 88.1 g/mol, ρ = 0.90 g/ml, LEL = 2.0 %v/v.

To obtain 50 %LEL (c = 1.0 %v/v) vapour of Ethyl acetate in the 3-litres calibration chamber insert

of liquid Ethyl acetate.

If the flashpoint of the liquid is less than 25 °C the value of the amount to be inserted into the 3 litres calibration chamber to obtain 50 %LEL is printed below the value of the density.  It is marked by a subsequent “v” (for volume).

Example: n-Hexane: 81 v

You need to insert 81 microliters into the Dräger Calibration Chamber to obtain 50 %LEL of hexane vapour.

Column 5: Dens. g/ml

In this column the density ρ of the liquid in g/ml (= g/cm3) at 20 °C is listed. This value exists only for liquids, so gases are indicated by “Gas”.

Column 6: Boil. °C

This column is self-explaining, it shows the boiling point of the substance in °C (at 1013 mbar).

Below the boiling point given in °C the boiling point is printed in °F. This value is marked by a subsequent “°F”.

Column 7: p20 mbar

Vapour pressure p20 of a liquid at 20 °C given in mbar (= hPa). Vapour pressure is only defined for liquids. So for gases instead of the vapour pressure you will find the marking “Gas” in this column.

The vapour of each liquid forms a pressure which depends on the nature of liquid and the liquid’s temperature. If the vapour pressure is low, the liquid evaporates slowly and thus only produces low vapour concentrations (for such flammable liquids the flashpoint is usually high). The maximum vapour concentration cmax (called saturated vapour concentration), which can only form in closed containments, can be estimated by dividing the given vapour pressure by the environmental atmospheric pressure.

Example: n-Nonane, p20 = 5 mbar, so

So at 20 °C no vapour concentrations higher than 4900 ppm n-Nonane can exist. Only higher temperatures may produce higher vapour concentrations. Since the Lower Explosion Limit is 0.7 %v/v even in a closed containment at 20 °C no explosive vapour/air-mixtures of n-Nonane can form.

It is essential that the “calibration chamber formula” does not apply for substances with a low vapour pressure, e.g. dosing to obtain 0.6 %v/v of n-Nonane vapour at 20 °C is not possible.

Column 8: Flpt. °C

This column shows the flashpoint of flammable liquids. Flammable gases do not have a flashpoint and are marked by “Gas”. Gases or liquids being non-flammable are marked by ‘n.a.’.

The flashpoint is defined as the temperature of a flammable liquid which (in a closed containment) is needed to obtain an ignitable vapour concentration above the liquid’s surface.

If ambient temperature and liquid temperature are clearly below the flashpoint (e.g. 10 °C lower), the liquid cannot be ignited.

Example: n-Nonane, flashpoint 31 °C, is not ignitable at 20 °C.

The relatively high flashpoint of n-Nonane is arising from its low vapour pressure. As already shown it is not possible to produce vapours of 100 %LEL under normal conditions (20 °C).

As the flashpoint is a temperature you can also convert a flashpoint F given in degrees Celsius into a flashpoint F given in degrees Fahrenheit using the conversion

Example: n-Nonane, flashpoint is 31 °C,

Below the flashpoint F given in °C the flashpoint is printed in °F. This value is marked by a subsequent “°F”.

Example: n-Nonane, flashpoint 88 °F

Columns 9, 10 and 11: LEL

These columns show the lower explosion limit in %v/v. Non-inflammable gases and liquids are marked by ‘n.a.’. If there is a void field this indicates that the LEL is unknown. Three values – if available – are listed here:

Germ.: Source: Brandes, Möller (PTB): Safety Characteristic Data, Vol. 1: Flammable Liquids and Gases, Wirtschaftsverlag NW, 2nd Edition, 2008

IEC: Source: IEC 60079-20-1: 2010 “Explosive atmospheres – Material characteristics for gas and vapour classification“

USA: Source: NFPA Fire Protection Guide to Hazardous Materials, 14th edition, 2010 (includes NFPA 497).

The NFPA LELs occasionally deviate from the mentioned ones because the apparatus and procedures to determine the LEL are differently standardized in the USA.

If there is no LEL available from these three sources, LELs from material safety data sheets or chemical catalogues are printed in column 9.

These LELs however are indicated by an additional asterisk (*).


By means of the mol weight (column 4) you can convert the LEL to g/m3 by multiplying the LEL given in %v/v with the mol weight M and dividing it by 2.4.

This conversion is valid for 20 °C.

Example: n-Nonane, M = 128.3 g/mol, LEL = 0.7 %v/v, so

The LEL of n-Nonane is 37.4 g/m3.

Below the LELs given in %v/v the corresponding values given in g/m3 are listed. They are enclosed in parenthesis.

Column 12: AIT °C

This column shows the auto-ignition temperature (AIT) of flammable gases and vapours. For non-flammable substances this column shows “n.a.”.

If known, the explosion group with subgroup, IIA, IIB or IIC (acc. To standard EN 60079-0), is listed in the 2nd line. If the ignition temperature is known, the 3rd line contains the temperature class. Electrical devices to be operated in hazardous atmospheres containing the considered flammable substance must at least be marked with the given explosion group and temperature class:


Allyl alcohol: AIT = 375 °C, IIB T2.

An electrical device must at least be marked IIB T2. Devices marked IIA T2 or IIB T1 are not allowed to be used in atmospheres where Allyl alcohol is present in potentially explosive concentrations.

Column 13 and 14: TLV Germ. And TLV USA

If available this column lists toxic limits as threshold limit values (TLV) or workplace limit values (WPL) in ppm.

TLV Germ.: Source: TRGS 900, update in September 2012.

TLV USA: Source: OSHA. If no OSHA value available: NIOSH

Commonly the TLVs are average values, but sometimes ceiling values (marked by a “c“) are listed. In no case ceiling values are allowed to be exceeded.

If neither the TLV Germ. nor the TLV USA is listed this does not necessarily mean that the considered substance is not toxic. Short-term limit values have not been regarded in this gas list.


By means of the mol weight (column 4) you can convert the TLV to mg/m3 by multiplying the TLV given in ppm with the mol weight M and dividing it by 24.

This conversion is valid for 20 °C.

Example: n-Nonane, M = 128.3 g/mol, TLV = 200 ppm:

The TLV is 1069 mg/m3.

Below the TLVs given in ppm the corresponding values given in mg/m3 are listed. They are enclosed in parenthesis. As these figures are exactly calculated they may slightly be different from officially issued values which are frequently rounded.

Column 15: Detectable by …

This column lists the transmitters by means of which the considered substance is detectable. This information is self-explaining. Especially the term “P 5000 … GP” indicates the non-explosion-proof (“general purpose”) version of Polytron 5000.

Column 16: Suitable measuring ranges

PEX 3000, SE Ex, P 5200 and P 8200 For catalytic bead sensors and transmitters the full scale deflection is always 100 %LEL. The 10 %LEL sensor can also be used for the detection of the listed substance, in this case the measuring range then is 0 … 10 %LEL.

P IR type 334 and P IR type 340 If the substance in consideration is stored in the transmitter’s EPROM and so is directly selectable from the gas library it is marked by “Gas-Library”.

The minimum and maximum f.s.d. in %LEL is listed. Separated by a “//” mostly the lowest f.s.d. is also listed in ppm.

A question mark indicates substances which are assumed to be detectable but have not been verified so far.

Dräger PIR 3000 The full scale value is always 100% LEL. Other measuring ranges are not suitable. A question mark indicates substances which are assumed to be detectable but have not been verified so far.

An exclamation mark indicates those substances for which a special calibration routine has to be performed.

Dräger P 5700 type 334 and 340 With this transmitter only the given full scale values are configurable.  So, “50 + 100 %LEL” means that full scale values of e.g. 70 or 80 %LEL are not configurable.  A question mark indicates substances which are assumed to be detectable but have not been verified so far.

Dräger PIR 7000 type 334 and 340 The listed measuring ranges are comparable to those of PIR Type 334 or 340. A “(§)” indicates substances being surely detectable but not yet having undergone verifying measurements – so no calibration hints can be issued so far. A question mark indicates substances which are assumed to be detectable but have not been verified so far.


Since measurements in our application laboratory are an on-going routine one can expect to have calibration data at a later date.

Pulsar Measuring ranges always are 1 and 4 / 8 LELm, 1 LELm is possible e.g. by the duct version.

Polytron 7000 and Polytron 8000 The minimum, standard, and maximum full scale deflections are listed. If the substance considered is not stored in the sensor’s EEPROM the full scale deflection values have to be multiplied by the given factor.

Example: Morpholine with Polytron 7000 and sensor NH3: “50 / 100 ppm x 4” means that the configured f.s.d. of 50 or 100 ppm NH3 corresponds to 200 or 400 ppm Morpholine. So when applying Morpholine to the sensor the reading has to be multiplied by factor 4 to obtain the true concentration.

Concerning the sensors OV1, OV2, H2S, and NH3, additionally the gas type to configure is recommended:

Example: 1-Hexene: “as Aald x 2” means:

To measure 1-Hexene configure for Acetic aldehyde, calibrate for Acetic aldehyde and multiply the reading by 2 to have the true concentration of 1-Hexene.

In some cases this factor may even be 0.5, so the reading has to be divided by 2.

Column 17: Important Remarks

Here you will find remarks concerning sensor poisoning by corrosive or polymerizing influences for catalytic bead sensors as well as information about response times (t20, t50).

Measuring performance

If the considered substance is subject of a measuring performance certificate (“measuring function for explosion protection”) this is indicated by “Performance Approval”.

Furthermore there are remarks like e.g. “detectability expected” or “on request”.

Also, the relative sensitivities S in respect to the target gas might be of special interest.

For electrochemical sensors the given relative sensitivities S are only valid for new sensors and the values might fluctuate about < ± 30 %. An “L” in parenthesis indicates that this sensor is only suitable to be used for leak detection.

Example: OV1-sensor for Butylene oxide: “S = 0.4 (L)” means the sensitivity of the OV1-sensor exposed to Butylene oxide is 40 % compared to ethylene oxide. For Butylene oxide this sensor should only be used for leak detection purposes.

What is leak detection?

A leak is an unpredictable abnormal release of gases or vapours of higher concentrations.

A leak has to be regarded as an exceptional event of a relative short duration.

In case of normal operation there is only clean air (without even low concentrations of the target gas or vapour).

A gas detection system for leak detection is not to measure a gas concentration but to give alarm reliably if a preset alarm threshold is exceeded.

That is why for leak detection rather the t20 or t50 response times are relevant instead of the t90-time. The given measuring ranges marked by “(L)” have to be interpreted as a range where an alarm threshold of the control unit can be set (choose e.g. 20% or 40% of full scale deflections).

After a gas release a leak gas detection system needs to be checked for proper function.

Mixtures of gases and vapours

Not to expand this gas list unnecessarily, only pure substances, but not mixtures of gases and vapours, are listed. This is especially true for mixtures of flammable solvents and fuels which are differently blended by different manufacturers.

For %LEL-measurement the gas detection instrument has to be calibrated for those substances in the mixture, which are detected with the least sensitivity. From this guideline calibration procedures based on pure substances can be derived. For example to detect Kerosene commonly a Nonane-calibration is recommended.  Moreover, a catalytic bead sensor calibrated for n-Nonane is also very suitable to detect numerous hydrocarbon mixtures such as gasolines, petrols, aviation fuels and jet petrols as well as Naphtha, Solvent Naphtha, Varnish Makers & Painters Naphtha (VMPN), White Spirit, etc.

However, whether such a calibration leads to safe detection in an individual application can only be derived from suitable Material Safety Data Sheets or needs to be verified by according measurement tests in the laboratory.