SINGAPORE - Facing down an angry mob may seem a scary prospect but for officers of the Police Tactical Unit (PTU), it is all in a day's work.

Armed with P4 rifles, officers can use the less lethal weapon to fire projectiles or pellets filled with an irritant similar to tear gas.

The pellets also contain paint to mark rioters for identification.

The unit had introduced an upgraded version of the P4 weapon in May 2015, after a prototype was unveiled at the Police Workplan Seminar and Exhibition in April that year.

Several innovative improvements were made to suit their operational requirements.

For example, the new weapon has a battery-operated hopper, to efficiently feed rounds into the chamber.

There is also a higher-capacity magazine that can store more rounds.

The P4 is one resource in the PTU's array of less lethal responses in handling riots.

A unit under the Special Operations Command, the PTU was formerly known as the Police Task Force.

It helps maintain public order, from dealing with civil disturbances to responding to emergency situations such as violent riots.

A police riot squad was first formed in the 1950s in response to the Maria Hertogh riots, which was the first major post-war riots in Singapore.

Accompanied by their signature red trucks often seen in the vicinity of crowded hot spots such as Orchard Road and Clarke Quay, officers from the PTU also perform security-related duties.

These include searches for armed criminals, illegal immigrants and responding to terrorist incidents.

Police officers train to become a member of the elite team at the Home Team Tactical Centre in Mandai Quarry Road.

Superintendent of Police Roy Shafiq Aw Abdullah, Commanding Officer of the Special Operations Training Centre, said PTU officers are put through realistic training scenarios to ensure that they are able to perform under duress.

"Not only do the troopers have to be physically fit, they have to be mentally alert during incidents so that they can deal with them effectively," he said.

During training, PTU officers have only three minutes to be fully geared up, while under pressure from their instructors.

This simulates a real scenario, when they have to respond to an emergency.

The full PTU protective gear consists of five things - leg guards, vest, shoulder and arm guards, gloves and helmet.

Each officer also has a baton and a gas mask.

They regularly take part in anti-riot drills to maintain their skills. In such drills, they are confronted by role-players in realistic riot scenarios.

During these sessions, they train to hold firm as one unit, and not allow the mob to breach their line.

They also employ the use of the P4 and tear gas shells to control the rowdy and violent crowd.

Accompanied by their peers and paws from the K-9 unit, they counter the rioters, dispersing most and arresting some of them.

PTU officers have to undergo gas confidence training as well, where they are exposed to the effects of the tear gas so they are prepared for the sensations should it be deployed in a real situation.

The day I cried on the job

The first time I teared on the job was when I was exposed to tear gas, or CS gas, which is made with the chemical compound 2-chlorobenzalmalononitrile.

It is one of the non-lethal responses officers from the Police Tactical Unit (PTU) can employ when handling violent rioters.

PTU officers have to undergo a gas confidence training session where they are familiarised with the sensation of being exposed to tear gas. This is so they are not caught off-guard should tear gas be deployed in a real situation.

On Friday (Oct 12), I joined the PTU officers for a session in a tear gas chamber.

Before entering, we were given filters to fix onto our full-face gas masks that have rubber edges that press firmly on the face.

We sat in a U-shaped formation and for five minutes were exposed to tear gas.

There was a cool sensation when the gas first hit the skin but soon there was a burning sensation and my skin felt itchy.

Soon it felt like I was being poked by many small needles.

I could feel it on my hands, the tips of my fingers, my neck and all parts of my skin that were exposed.

That burning sensation subsided after a while, but that was not all the gas had in store for us.

As part of the gas confidence training, we had to stand up, remove our masks, and recite our full name and NRIC numbers, before leaving the room.

I took a deep breath, and removed my mask.

It was not too bad initially.

I began: "Fabian Koh..."

And then it hit me like a slap to the face.

The tears started flowing involuntarily.

And mucus from my nose, and saliva from my mouth.

My body was trying to fight the irritants, which triggered these fluid responses.

Because the gas was made up of particles, we were told not to rub our skin or it would just spread the particles out, intensifying the effects even more strongly.

All we could do was walk around and let the breeze work its magic.