Security forces are legally allowed to use tear gas for crowd control, but there are strict international guidelines around its use and the way it can be deployed against civilians for crowd control.

Journalists covering demonstrations should be aware of the effects of tear gas and how to respond when affected.

How does tear gas work?

Typical RCAs (Riot Control Agents) such as tear gas are delivered by either a spray or a grenade canister fired from a baton gun. The canisters themselves can be hazardous as they usually generate a lot of heat and will cause nasty burns if handled. If they are fired at close range, they can cause serious damage to a person’s body and have resulted in death.

When chemicals used in tear gas react with moisture they cause a burning sensation, meaning that the eyes, skin and lungs are extremely susceptible. Oil-based creams, sunscreens and make-up will also absorb tear gas, so avoid wearing these when covering protests where it might be used.

Tear gas attacks the lungs, so if you suffer from any respiratory diseases, including asthma, you should seriously consider the potentially dangerous effects this may have on your condition.

Streaming and burning of eyelids and throat as well as excessive coughing are all reactions to tear gas. An excess of mucus coming from the nose, eyelids and throat is also common. People often report that they feel disorientated and dizzy just after breathing it in.

The effects usually wear off within an hour, although the feeling of burning and highly irritated skin may persist for hours.

How to protect yourself

A gas mask (often called a respirator) is the best tool to protect yourself. They are not cheap, but they'll allow you to cover the story safely. They are subject to export licences in some countries, so ensure you have the correct paperwork to travel with them.

A gas mask consists of a rubber mask with a canister and filter fitted to the side. It is fitted to the size and shape of your face, and you should not assume that yours will fit someone else. Ensure you have a spare canister, as they do need changing after several hours (this depends on the make and model of the gas mask as well as how long it has been used).

If you already have a gas mask, make sure it is working properly and is correctly fitted. Any masks purchased online or in military surplus stores should be checked by an expert to ensure they work correctly.

The next best thing after a gas mask is an escape hood, which is cheaper and is not subject to the same export rules.

You can also use a builder's respirator that covers your nose and mouth – but make sure that you use appropriate filters. Failing that, a dust mask for DIY and building and airtight goggles will provide some degree of protection.

Myths and misconceptions

Sometimes, it's hard to see through the myths surrounding tear gas protection. Reports, photographs and videos show protesters using improvised methods to counter the crippling effects, including tying plastic bottle and even bras to their faces. While they make for an amusing photo, these are not effective ways of countering this non-lethal chemical weapon.

INSI spoke to chemical weapons experts SecureBio about other homemade methods, which should be avoided.

1. Soaking a bandana or cloth in apple cider vinegar and tightly covering your mouth with it

The acid contained in the vinegar does not provide enough, if any, protection to counter the effects of tear gas.

2. Smearing lime or lemon juice on the inside of a cloth and tightly covering your mouth with it

This supposedly works on the same principal as the apple cider vinegar, but again should be avoided.

3. Soaking a bandana in water and tightly covering your mouth with it

Many RCAs come in the form of crystals, which react with water. Using small amounts of water (such as a wet handkerchief) immediately after exposure to CS gas is likely to reactivate these crystals and may prolong the effects.

3. Smashing up charcoal, lining a wet bandana with the dust, and tightly covering your nose and mouth with it

The charcoal supposedly filters out CS gas, but there is no evidence to support this.

4. Smearing toothpaste under your eyes

As RCAs and toothpastes are made up from a wide range of chemicals, using various manufacturing methods, it is nearly impossible to accurately predict the reactions that would take place.

5. Sniffing a freshly cut onion

Breaking an onion in half, sniffing it and getting it close to your eyes does not reduce the irritation, and it is likely to make you cry just as it does when you are peeling it.

What to do if you get tear gassed

If you have a gas mask, or a mask and goggles, put them on. You may then be able to continue working in the gas. Be aware that you will still need to wash yourself and all clothes as the gas will remain on you, your clothes and your equipment.

If you have no protection, cover your mouth and nose with a handkerchief or cloth or use the inside of your coat to protect your airway (the outside of your jacket is likely to be contaminated).

Stand in the fresh air and allow the breeze to carry away the CS gas.

Keeping your arms outstretched which will help CS gas to come off your clothing.

Try to get to high ground – most RCAs are heavier than air, so the highest concentrations tend to sit nearer to the ground.

Remember that the gas will impregnate clothing for many months, so any clothing that may have been contaminated should be immediately washed several times or discarded.

Any exposed skin should be washed with soap and water. Shower first in cold water, then warm water. Do not bathe.

Don't rub your eyes or face, or this will reactivate any crystals.

Some of the above information has been provided by SecureBio.

Photo: People walk during a rally by the labor unions in Istanbul, Turkey. A day earlier, riot police cordoned off streets, set up roadblocks and fired tear gas and water cannons to prevent anti-government protesters from an effort to return to Taksim Square. (AP Photo)