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How long does it take chlorine gas to dissipate?

By
Updated on November 14, 2023
Written by
Marie Cookson
Based in Manchester, Marie is one of the writers at HouseFresh and our resident dust expert. She works together with our in-house researchers and our Managing Editor to produce in-depth articles offering practical advice on how to tackle indoor air quality issues.
TL;DR

Chlorine gas is highly toxic and can stay in the air for long periods of time. 

That said, it can dissipate faster if the amount of gas released is minimal, and the space is well ventilated with fresh, clean air circulation. 

It’s important to get away from the affected area as soon as possible. Equally, if you’re experiencing any symptoms following exposure, seeking medical attention will help mitigate any serious, long-term health problems.

Most of us are familiar with the strong smell of chlorine that comes from a dip in the swimming pool. The chlorine helps to keep the water clean and is entirely safe. 

But chlorine gas is a different story. 

When chlorine compounds react with other substances in the environment, chlorine gas (Cl2) is formed. For example, if bleach is mixed with other cleaning agents, such as ammonia or acetic acid (present in vinegar), it can release chlorine gas. 

When chlorine gas enters the air, it can pose a serious health risk. Exposure may be through inhalation, or bodily contact, and it can damage your lungs, skin, and eyes – this is why you should never mix household cleaners.

A bit like bleach, chlorine gas has a very strong odor, but you can also see it in the atmosphere due to its green or yellowish tint. It is heavier than air, which means that it tends to sink and settle closer to the floor or lower ground levels and spread rapidly.

Inhaling or coming into contact with chlorine gas can lead to health problems, from a sore throat to serious breathing difficulties. 

 

The reactive nature of chlorine gas means that it can stay in the air longer than many other gasses. However, there are various factors that affect how long it does remain present. These primarily include:

  • Concentration levels and how much gas has been released 
  • Size of the space, for example, whether the area is big or small
  • Degree of ventilation and fresh air circulation 
  • Atmospheric/environmental conditions, including temperature and humidity 

Chlorine gas can stay in indoor air for just a few minutes or hours (between 1-8 on average) before dissipating. This is generally when the concentrations are fairly low and there is adequate ventilation.

Yet in some cases, the gas can linger for several days, weeks or even months, especially when it has been released into an enclosed space with little fresh air circulation.

Equally, low temperatures coupled with high humidity can mean that the gas remains airborne for longer as both of these conditions will slow down the evaporation process. The reverse is also true; high temperatures and low humidity can speed up the process and cause the chlorine gas to dissipate faster.

Essentially, chlorine gas will stay in the air until it is removed by ventilation or the processes that contribute to its natural decay. 

Yet even when chlorine gas has fully dissipated from a space, the area may not be completely safe. This is because it can settle on surfaces or be absorbed into materials like clothing and carpets. Such materials may then continue to release chlorine gas into the air and remain a health risk.

How do you neutralize chlorine gas in the air? 

There are a few ways to counteract the impact of chlorine gas:

1. Ventilate the space

Opening windows and doors as soon as possible means that fresh air from the outside is able to replace stale, toxic air quickly. The increased airflow helps to reduce concentrations of chlorine gas particles that can invade your home.

While natural ventilation like opening windows is effective, you could also use mechanical systems, such as fans. This will further help to bring in fresh air from outdoors and distribute it around the area.

2. Use activated carbon filters 

Activated carbon filters are used in the home and in businesses, such as hotels and restaurants. They’re highly efficient at trapping harmful airborne particles like chlorine gas. After the filter has captured the particles, it’s then able to release clean, fresher air back into the space. 

Running an air purifier with an activated carbon filter is one of the most effective ways you can use this kind of technique for neutralizing chlorine gas. Be sure to check out our list of the best air purifiers we tested in 2023 for inspiration.

3. In extreme cases, evacuate and call 911

In extreme situations, it may be the case that you need to completely evacuate the space and call a trained professional. They will be able to neutralize the chlorine gas quickly while using the proper safety precautions and equipment. 

If you suspect you do need further assistance, be sure to contact a professional straight away as waiting too long might have serious implications for your health.

Tip

If you need further assistance, don’t hesitate to contact a professional organization for expert guidance and advice:

📞 Call or email the Centers for Disease Control and Prevention

📞 Call the emergency response helpline at the Agency for Toxic Substances and Disease Registry

8 Steps to follow when exposed to chlorine 

Follow these steps:

  1. If the chlorine gas was released from household cleaners, open windows and doors to let fresh air in and circulate around the space.
  2. Get away from the area so that you can also breathe fresh air.
  3. Get the chlorine off your body. Firstly, remove accessories, jewelry, and all items of clothing but avoid pulling the clothing over your head. If you have to undress this way, hold your breath and close your eyes and mouth. If possible, pull the clothing down your body or cut it off to prevent further exposure and damage to your body.
  4. Place everything in a plastic bag.
  5. Remove contact lenses if you wear them and place them with your clothing. Do not put the lenses back in later.
  6. Ideally, get in the shower as this is the most effective method for removing chlorine. Using mild soap (you don’t need a special soap) and warm water, wash your face, hair, and hands, then the rest of your body, starting with your head. This includes armpits, groin, and feet. Do not scrub. Finish off by rinsing in plain water, yet avoid letting it run into your eyes, mouth, or nose.
  7. If you can’t see properly or your eyes are burning, use lukewarm water to flush your eyes for 10-15 minutes. Do not use eye drops at all.
  8. Dry off carefully. Start with your face, then tilt your head back to dry your hair. Finally, dry down your body.

Chlorine exposure symptoms

Chlorine forms acids when it comes into contact with water. Since the human body contains many areas that are wet or moist, such as the eyes, throat, and lungs, chlorine exposure can be especially harmful.

There are several factors that affect the severity of symptoms, and the amount of chlorine you were exposed to is critical. Minor exposure, for example, could mean fewer or less serious health problems. Whereas more significant exposure can cause major health issues, and even lead to death. 

Similarly, the length of time you were exposed to the chlorine, as well as how you were exposed to it (through inhalation or touching, etc.) can also affect the degree of reaction. 

🚩Throat. A sore throat is the most common, but you might experience a burning feeling, which may be accompanied by burning in your nose or chest.

🚩Eyes. Eye irritation and redness are also two of the most common symptoms, as are red or watery eyes, and blurry vision.

🚩Skin. Chlorine exposure can lead to numerous skin complaints, including pain, irritation, itching, redness, rashes, and blisters. 

🚩Respiratory system. Breathing difficulties include coughing, wheezing, chest pain or tightness, and fluid buildup in the lungs. It’s important to note that people with asthma or other chronic lung disease may be more vulnerable to the effects of chlorine exposure. In serious cases, exposure may even lead to respiratory failure and death.

🚩Gastrointestinal system. Following chlorine exposure, gastrointestinal symptoms like diarrhoea can appear almost straight away, or they may take a number of hours.

🚩Nervous/neurological system. Symptoms that affect your nervous system include light-headedness, confusion, and headache. You might also experience nausea and vomiting.

Whether your symptoms are mild, moderate, or severe, it’s vital to seek medical attention as soon as you can. If symptoms aren’t treated properly, you may go on to suffer from long-term effects and develop chronic health problems. Yet with supportive medical care, most people fully recover from chlorine exposure.


Final thoughts

Chlorine gas can cause various health problems, and the length of time it stays in the air depends on several factors. These include how much gas has been released, the size of the space it has been released into, and the degree of ventilation. 

Yet there are effective ways to reduce exposure. Chlorine gas can dissipate more quickly, for example, when ventilation is increased. Plus, the use of activated carbon filters can help to facilitate fresh, clean air circulation, which will further minimize exposure.

SOURCES

About the author

Marie Cookson

Based in Manchester, Marie is one of the writers at HouseFresh and our resident dust expert. She works together with our in-house researchers and our Managing Editor to produce in-depth articles offering practical advice on how to tackle indoor air quality issues.