Chlorine Gas (Cl₂) Measure Icon

Chlorine / chlorine gas (Cl₂)

Chlorine (Cl₂) is a toxic greenish gas with high reactivity. In low concentrations it irritates the mucous membranes and respiratory tract, in high concentrations it has a corrosive effect.

Can be measured with:

✓ Measurable with the air-Q Science or Chlorine (Cl₂) single sensor.


Chlorine / chlorine gas (Cl₂) is a gas at room temperature, but in nature it occurs almost exclusively in bound form, as it has a high reactivity with almost all other elements. Exceptions are volcanic gases and higher layers of the atmosphere in which chlorine gas occurs in molecular form.  

Combined chlorine, on the other hand, is found very frequently. It is a component of seawater and the table salt (sodium chloride) obtained from it.

In industry, chlorine is used in liquid and combined form in the production of chemicals and medicines. For example, it is the starting product for bleaching agents and disinfectants as well as for the plastic PVC. For this purpose, it is obtained chemically by electrolysis.

In everyday life, chlorine enters the air we breathe primarily through the use of cleaning agents and disinfectants. However, there are also workplaces, such as swimming pools, where people are exposed to higher concentrations of chlorine gas. In addition, storage sites for chlorine gas containers are a potential source of danger.

Chlorine damages the respiratory and digestive tracts at concentrations as low as 0.001%. From approx. 0.5%, chlorine gas has a lethal effect on humans. Therefore, chlorine gas containers must always be tightly closed and located in safe places. These are rooms that are well ventilated and protected from heat, open fire and moisture.

In the case of cleaning agents and disinfectants, the instructions on the packaging should be followed urgently to prevent irritation or burns.

Limits of chlorine in the air:

Since chlorine is corrosive to mucous membranes and respiratory tract even in low concentrations, there are legally regulated limits for handling the gas. The occupational exposure limit (OEL) for chlorine is 0.5 ppm. A chlorine limit of 0.3 mg/l applies to drinking water. Chlorinated drinking water loses a large part of the chlorine in the form of chlorine gases through evaporation. Before drinking, therefore, the water can be completely dechlorinated by boiling or letting it stand for a short time.

Designationning Chlorine / chlorine gas limits (Cl₂)
Odorthreshold 0.02 ppm - 1 ppm
Workplacelimit value (AGW) 0.5 ppm (= 1.5 mg/m³ air)

Consequences of too high a concentration:

In dissolved form in water, it is suspected of increasing the risk of bladder cancer. For this reason, legal limits apply to its use. Chlorine also outgasses from water.

In gas form, chlorine (Cl₂) is toxic and has an irritating effect. Inhalation of chlorine gas can lead to respiratory disorders, dizziness and nausea. Air with a greatly increased chlorine content causes burns to the mucous membranes and respiratory tract within a few minutes. For this reason, special protective measures apply to workplaces where chlorine is used.

Formation of chlorine:

Chlorine can be isolated from its natural bound form by chemical processes. This includes, for example, extraction by chlor-alkali electrolysis. In this process, a sodium chloride solution is separated into chlorine and sodium hydroxide solution by means of an electric current.

Sensor used:

Chlorine is measured in the air-Q by means of an electrochemical sensor. Cl₂ molecules react with the surface of the sensor and cause a measurable current. The sensor used has a very high accuracy. The disadvantage of the sensor, as with all electrochemical sensors, is cross-sensitivities - so the sensor also reacts strongly to fluorine and bromine and somewhat to sulfur dioxide, chlorine dioxide and ozone.

Measure chlorine gas:

Measure chlorine as well as other gases and pollutants in the room air in real time with the air analyzer air-Q. The chlorine sensor can be ordered in the store.

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