Chlorine guide
Chlorine: a compact overview of the chemical element
Chlorine is a gaseous substance that many people have mixed feelings about. On the one hand, the news of chlorine gas accidents is a deterrent. Because chlorine is toxic. On the other hand, we plunge into the chlorinated pool to refresh ourselves without a second thought. So what is chlorine all about? What are the benefits of chlorine and what are the dangers? What safety requirements does handling chlorine entail and what measures should be taken in the event of an emergency – a chlorine leak? This compact overview provides information about one of the best-known chemical elements and gases.
- Number 17 under the magnifying glass
- Appearance and odour
- The reactivity of chlorine
- Chlorine – chemical and physical properties
- The use of chlorine
- Chlorine and the environment
- The dangers of chlorine
- The toxicology of chlorine
- Access via the airways
- Acute and toxic effects due to toxic chlorine
- Chronic toxicity – the result of prolonged exposure to chlorine
- Chlorine poisoning – what to do!
- Exposure to chlorine / eyes
- Exposure to chlorine / skin
- Exposure to chlorine / respiratory organs
- Exposure to chlorine / digestive tract
- The correct handling of chlorine
- Measures in the event of chlorine leakage
- Measurements and controls are indispensable
- Measuring chlorine – but how?
- Use different devices from the specialist Compur Monitors
Number 17 under the magnifying glass
Chlorine is one of the classic chemical elements that pupils learn about in chemistry lessons using the periodic table. The symbol for chlorine is the abbreviation “Cl”. The atomic number of the chemical element is 17. Chlorine is a substance that occurs as a gaseous element under normal conditions. It is therefore categorised together with bromine, fluorine and iodine in the group of halogens. It also belongs to the group of inorganic gases. However, chlorine can also change its physical state: Gaseous chlorine becomes liquid when pressurised.
Chlorine is very reactive. In nature, it therefore only occurs as a compound. In chemistry, however, the element is indispensable. To do this, it has to be extracted from one of its compounds using a lot of energy. Usually from common salt or potash.
Appearance and odour
The characterisation of a chemical element also includes its appearance and odour. In the case of chlorine, these are particularly typical. The colour of the chemical substance is a toxic – the name says it all – yellow-green! Incidentally, this is also where the name of the gas comes from, as the Greek word for “light green” is “chloros”. The odour is pungent. You can clearly smell whether water has been chlorinated, for example – be it in the pool or the tap water, which is usually given an extra dose of chlorine by the local authorities after contamination (e.g. by germs).
The reactivity of chlorine
Chlorine is one of the most reactive elements we know of today. The reason for this is the gaseous structure of the molecule, which is made up of two atoms. It means that chlorine forms stable compounds with almost all molecules or chemical substances. This typical behaviour of chlorine has two consequences: Firstly, it is the reason why chlorine is particularly toxic. On the other hand, the reactivity of chlorine also means that the element exists in the wild exclusively as a compound and hardly ever as an element. Many such compounds can be recognised by the suffix -chloride. The best example of this is sodium chloride – the classic table salt, which is found both in the sea and in our bodies. The element does not occur on the earth’s surface.
Chlorine – chemical and physical properties
Chlorine is a non-flammable gas. However, it can intensify fires through chemical reactions or contribute to starting fires in the first place or intensifying a fire that has already broken out. Another typical characteristic of chlorine is its ability to oxidise strongly. This is already the case at normal temperatures. This is particularly pronounced in the heat. Chlorine reacts with almost all chemical elements and numerous inorganic and organic compounds. The water solubility of chlorine, however, is rather moderate.
Physical values of chlorine are, for example, the melting point of -100.98 °C and the boiling point of -34.1 °C. The critical temperature is 144 °C. The gas density of chlorine is 3.000 kg/m³ at 15 degrees Celsius, the vapour pressure, for example, is 6.8 bar at 20 degrees Celsius. The water solubility is 14.6 g/l at a temperature of 0 degrees.
The use of chlorine
The element chlorine is used for a whole range of applications. Around a third of chlorine utilisation is used for the production of vinyl. Chlorine is also an important input product in the production of other plastics, pesticides or medicines, for example in the production of titanium. Chlorine is also a strong bleaching agent. The term “chlorine bleach” is well known. The bleaching effect of chlorine is due to the fact that the introduction of chlorine into water also produces hydrochloric acid, among other things. This oxidises and bleaches. In the past, paper was bleached with chlorine, but today less harmful methods are usually used.
Chlorine is also valued for its disinfecting effect. A typical area of application is water treatment – both drinking water and swimming pool water. Undesired germs are killed by the chlorine. Care is taken to ensure that the chlorine is used in concentrations that do not cause any health problems. However, eye irritation after swimming in chlorinated water is not uncommon. Therefore, alternatives are also used for chlorination. The two typical substances are ozone and chlorine dioxide. However, these are even more toxic than chlorine.
Chlorine and the environment
The toxicity of chlorine and some chlorine compounds naturally leads to discussions about the environmental compatibility of chlorine. The industry is endeavouring to replace chlorine with alternatives wherever possible. Another option is not to extract chlorine from raw materials, but to recycle waste containing chlorine. This recycling has two advantages: Firstly, it reduces the need for chlorine from raw materials and secondly, harmful emissions from the incineration of chlorine compounds are avoided. However, it is still problematic that in many cases there is no substitute for chlorine. In most cases, recycled chlorine is too expensive and is not used for economic reasons.
The dangers of chlorine
Due to the physical and chemical properties of chlorine, it has a number of hazardous properties – both for the environment and for health.
One example of the high hazard potential of chlorine is the explosion hazard of the chemical element. This is particularly pronounced when chlorine comes into contact with catalytic surfaces. This danger can increase under the influence of heat, light and UV radiation. Typical representatives of these substances with which chlorine can react dangerously include ammonia and oxygen, acetylene and petrol, fats and fluorine, glycerine and rubber, phosphorus and hydrogen. Even contact with supposedly harmless substances such as linseed oil and wax can cause dangerous reactions due to the toxic chlorine.
The toxicology of chlorine
Elemental chlorine has a variety of harmful effects on the organism. Studies show that even traces of the element chlorine found in seawater accumulate in the organ systems of fish and crustaceans over the long term. Chlorine gains access to the body in different ways. However, access via the gastrointestinal tract and access via the skin are somewhat less relevant. The situation is different when chlorine is inhaled:
Access via the airways
Inhaling low concentrations of chlorine gas does not usually affect the lungs. Because chlorine is not very soluble in water, the mucous membranes of the throat, trachea and upper bronchi can act as a natural barrier against the chlorine. However, if a lot of the chlorine is inhaled, the fine air bubbles of the respiratory system, the alveoli, are also affected.
Acute and toxic effects due to toxic chlorine
Acute chlorine gas poisoning can cause lasting damage to health. As a typical irritant gas, it typically causes severe tissue irritation or even chemical burns. Contact with chlorine in the eyes and respiratory tract is particularly dangerous. Depending on the amount of chlorine gas inhaled and any pre-existing health conditions (possible allergies or asthma), there is a risk of severe and sometimes irreversible damage to the lung tissue. This damage can lead to lung oedema, which can be fatal.
Classic symptoms of acute chlorine poisoning are
- Irritation of the eyes
- Irritation of the bronchial tubes
- Shortness of breath and cyanosis
- Coughing
- Headaches
- Chest pains
- Problems with the gastrointestinal tract
- High or low temperature
- Nausea and vomiting
- Cramps and muscle pains
In some patients, these symptoms are still detectable three weeks after poisoning with chlorine gas. However, there are also patients who recover quickly and completely. However, a permanently hyperreactive bronchial system can also remain.
Liquid chlorine causes severe chemical burns on contact with the skin. Frostbite damage to the tissue is also a typical consequence.
If chlorine is swallowed in high concentrations, it can also cause chemical burns. This usually affects the stomach and oesophagus. However, chlorine ingestion can also cause disorders of the central nervous system and the cardiovascular system.
Chronic toxicity – the result of prolonged exposure to chlorine
The effects described above primarily relate to acute poisoning with corrosive chlorine – even at high concentrations. However, effects caused by regular contact with chlorine in lower concentrations – for example in certain occupations – are also highly relevant. Such exposure also causes irritation of the (usually upper) respiratory tract and impaired lung function. Such problems have not yet been proven below a concentration of 0.5 ppm chlorine. However, one long-term complication already mentioned, the hyperreactive bronchial system, is not caused by long-term exposure, but by acute poisoning. The complication seems to affect people who have a certain susceptibility, such as a previous illness or an allergy.
The influence of chlorine on reproduction, genetic damage and cancer was also investigated. The result of the studies: no correlations were found, but it is strongly recommended that existing limit values are strictly adhered to.
These values are:
- Occupational exposure limits / AGW values
- BGW value
- BAT value
In order to effectively comply with these values, close monitoring using modern measurements is of course necessary.
Chlorine poisoning – what to do!
There are a whole range of effective measures to minimise or prevent the consequences of chlorine gas poisoning. It is important that these are applied immediately after contact with the chlorine.
Exposure to chlorine / eyes
If the eyes have been contaminated by chlorine gas or an aqueous chlorine solution, immediate action must be taken to prevent long-term damage. As an immediate measure, the eye should be rinsed for at least ten minutes, making sure that the other eye is protected. The eyelids of the affected eye should be spread wide open. However, if the eye is contaminated by supercooled or liquefied chlorine gas, rinse briefly under cold water without spreading the eyelid. Contact lens wearers should not remove their contact lenses. As a general rule, consult a doctor immediately after rinsing!
Exposure to chlorine / skin
After exposure to an aqueous chlorine solution, any contaminated clothing must be removed. It is essential to avoid further contamination of the skin (both of the affected person and of first aiders). Skin wetted by chlorine should be rinsed under running water for at least ten to 20 minutes. Affected skin must also be treated by a doctor. If the skin is contaminated by liquefied chlorine or cryogenic gas, the affected person must first be removed from the immediate danger zone. Here too, self-protection has priority. Frozen clothing can be thawed and carefully removed by rinsing with cold water. The skin should also be rinsed with cold water. Dry heat or even rubbing is counterproductive. The affected skin should be covered with a sterile dressing. Ideally, the doctor should be called at the same time as all these measures are taken.
Exposure to chlorine / respiratory organs
Even when inhaling chlorine, the first measure is to move the injured person(s) to fresh air under self-protection. Physical exertion of the affected person must be avoided at all costs – even if the affected person states that they are symptom-free. The person should be carried or wheeled horizontally, and a semi-sitting position is recommended in the event of respiratory distress. An important measure is the deep and repeated inhalation of a glucocorticoid, or oxygen in the event of respiratory distress. Until the emergency doctor arrives, the person should be placed in a stable lateral position if unconscious and, in the event of respiratory arrest, ventilated with a breathing aid if possible for reasons of self-protection. In the event of cardiac arrest, the classic resuscitation measures – cardiac massage and artificial respiration – should be carried out. Ideally, a defibrillator should be used.
Exposure to chlorine / digestive tract
After swallowing, spitting out and rinsing the mouth are the first two measures. If the affected person is awake, they should drink about 200 ml of water. Vomiting should not be forced. If the person vomits spontaneously, this should be done in a prone position and with the head low to avoid inhaling vomit containing chlorine. Ingestion of chlorine also requires medical attention.
The correct handling of chlorine
Chlorine handling should be carried out in accordance with all applicable regulations. Some examples: Workspaces should be well ventilated – especially in the floor area. Eye showers and water curtains are important. Relevant production processes must be fully monitored. Gas systems must have safety valves. It goes without saying that compliance with specified emission limits is the be-all and end-all. Areas containing chlorine must be precisely labelled.Gas cylinders must be stored and used professionally and checked for leaks. Chlorine must be stored without risk of fire and protected from sunlight. Employees need appropriate protective clothing. The equipment also includes safety shoes, respiratory protection, eye protection and hand protection. Contaminated objects or pressurised gas cylinders may only be disposed of in accordance with the Waste Catalogue Ordinance (AVV).
Measures in the event of chlorine leakage
The following measures are useful:
- Ventilate
- Remove ignition sources
- Evacuate the area
- Warn the surrounding area
- Enter the area only with protective clothing and breathing apparatus
- Stop the gas leak
- Extract leaking gas
- Check gas concentration
- Prevent chlorine gas, which typically collects at floor level, or contaminated fire extinguishing water from entering the sewer system or cellars.
- Use water mist or fine spray jets.
- Notify authorities
Measurements and controls are indispensable
Professional installation of the gas system is the solid basis for safety in the company. It is also very important to have the process checked by specialists before commissioning. Staff must be professionally and precisely trained in handling the highly sensitive material and recognising potential faults at an early stage. Regular leak testing is important. However, not every leak or malfunction is easy for employees to recognise. This is why measuring devices and warning systems are an important investment in the safety of the company and its employees. The company needs reliable equipment in the endangered areas that recognises and reports gas leaks at an early stage. Gas detectors with alarm triggering are indispensable in order to minimise risks to buildings, people and the environment and also to fully comply with legal and insurance regulations.
Measuring chlorine – but how?
If you bear in mind that chlorine was even used as a combat gas during the First World War, it is easy to understand that chlorine gas may only be used under strict safety precautions. Nowadays, there are valuable measuring and warning devices that offer comprehensive safety. Outstanding here are devices that regularly check themselves with chlorine.
Good measuring devices have reliable sensor technology. They are very sensitive and extremely specific. Ideally, the sensors are particularly resistant to chlorine and its corrosive properties. Devices that have an integrated automatic self-test are particularly valuable. One example of this is the Statox 560 from Compur Monitors. The self-test with the target gas detects any faults in the gas detector at an early stage. This is a real plus in safety for the user. Long before the sensors fail, these self-tests can also detect a need for maintenance. This saves you a lot of time for inspection rounds, so that safety can also be realised efficiently and economically.
Use different devices from the specialist Compur Monitors
At Compur Monitors, we specialise in measuring devices that protect against hazardous substances. This is especially true for chlorine gas. We offer a range of different devices which, once selected according to requirements, comprehensively optimise the safety of companies from escaping chlorine gas. Stationary and personal gas detectors and tracers utilise the latest technologies to immediately detect and report chlorine gas through constant and highly precise measurements. Installation and familiarisation are straightforward. Nevertheless, our professionals provide competent and specific advice on the possible measuring devices and their ideal fields of application, correct handling and possible faults. Gas detectors – also and especially with regard to highly reactive and toxic chlorine – are a smart investment in a valuable asset: the safety of people, nature and operations.
Dr. Josef von Stackelberg
Managing Director COMPUR MONITORS GmbH & Co. KG
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