Jaralla, near Mosul - For a good while, it felt like another tedious guard shift for Chato Saeed, a Peshmerga soldier on the Kurdish frontline against the Islamic State of Iraq and the Levant group (ISIL, also known as ISIS). In the blistering afternoon of that mid-August day last year, the flat plains in this part of southern Nineveh resembled a mirage as heat waves simmered above the ground. Suddenly, Saeed, 34, and another fellow guard heard the whistling sound of a mortar attack.

As they ducked behind the sandbags erected to protect them from enemy fire, they heard a shallow explosion. A few seconds later, they peered through gaps between the sandbags and saw "something like a yellowish or whitish smoke" arising from the spot where the rocket had landed.

"My friend shouted, 'It's a chemical attack!' and ran down to take cover in the room below," Saeed told Al Jazeera. Saeed hastily untied the checkered white and black turban he was wearing around his neck and poured some water on it and covered his face hoping to protect himself from the gasses that the wind was sweeping towards him.

Soon, he ran out of breath. "I started feeling dizzy and then fainted," said Saeed.

He and 13 other wounded Peshmerga troops were taken to a small health facility in the nearby town of Makhmour. To this day, Saeed says he still suffers from an infection in his left ear and if exposed to strong sunlight "my face turns red and I feel like my skin thickens and I get rushes".

READ MORE: The US, the Peshmerga and Mosul

The gas attack that Saeed endured in Jaralla was just one of a rising number of such attacks launched by ISIL against Kurdish forces.

They know about the preparations for retaking Mosul, so they're resorting to chemical attacks more often than before to show their capabilities and power. Mahmoud Ali, head of a Peshmerga engineering unit

According to figures gathered from multiple military sources in Iraq's Kurdistan, ISIL used chemical attacks fewer than 10 times in the first year and a half after its dramatic expansion in northern and western Iraq began in June 2014.

But since the start of 2016, the group has staged at least 13 chemical attacks against Kurdish forces, utilising materials such as chlorine and sulfur mustard in these attacks.

Kurdish sources say the attacks have not been lethal but believe the increasing use of chemical attacks is designed to weaken the frontlines.

As Iraqi and Kurdish forces set their eyes on Mosul, where a military offensive is expected to attempt to retake northern Iraq's largest city from ISIL by the end of the year, more chemical attacks by ISIL 'are expected', according to sources in the Peshmerga forces.

"They know about the preparations for retaking Mosul, so they're resorting to chemical attacks more often than before to show their capabilities and power, and prove that they can protect and defend their area," General Mahmoud Ali, head of a Peshmerga engineering unit, told Al Jazeera.

His unit is the first one that arrives at a scene of a chemical attack to remove the shells and do an initial clean up of the site.

Despite the recurring attacks, Kurdish forces were until recently in dire need of gear to protect themselves against gas attacks by ISIL. During a visit in late May to Kurdish-controlled Makhmour, one of the areas most affected by ISIL chemical weapons, the officers and soldiers complained that, two years into the war, they were still ill-equipped and highly vulnerable to chemical assaults.

Major Luqman Abdulaziz said that his battalion of about 500 people had only a few dozen gas masks for protection. The masks were donated by Germany that had earlier in the year provided about 1,000 masks to the Kurdish forces, but Abdulaziz's unit managed to get only a few dozen.

"So far we have been relying on primitive ways of protection, using water tanks, towels or jamadani [traditional Kurdish head turbans] to protect ourselves every time there's a chemical attack," Abdulaziz told Al Jazeera back in May.

The problem is not only about protection, but also treatment of wounded personnel. In the Makhmour area, a barely equipped general-purpose health centre is the only facility to provide first aid to incoming wounded troops.

"We can only provide oxygen and hydrocortisone [a medication to treat skin conditions that reduces swelling, itching, and redness]," said Aso Aziz, administrative head of the Makhmour health centre.

IN PICTURES: Life on the frontline in Iraq

While ISIL's use of the internationally prohibited weapons has been mostly concentrated in the areas in the vicinity of Mosul, it also launched a gas attack in March on the Shia Turkmen-dominated town of Taza in Kirkuk province. As many as 50 civilians were wounded in that attack, according to Iraqi authorities.

Under the former regime of Saddam Hussein, Iraq had an active chemical weapons programme for years. The regime infamously used chemical weapons against its own Kurdish population as well as Iranian troops and civilians during its eight-year war with the neighbouring country.

Some of the veterans of Saddam's chemical weapons programme, such as Abu Malik, are believed to have played an important role in building ISIL's arsenal. Abu Malik, who joined ISIL's chemical weapons programme in the summer of 2014, was killed in an air strike by the US-led coalition near Mosul in January 2015.

General Ali says that ISIL has mostly relied on the chemistry labs at the University of Mosul, once one of Iraq's finest centres of higher education, to develop its chemical weapons programme.

But recently, ISIL appears to have moved the bulk of their chemical activities from Mosul University to residential areas to avoid attacks, says Hamish de Bretton-Gordon, a chemical weapons adviser to NGOs working in Syria and Iraq and former commanding officer of the UK Chemical, Biological, Radiological and Nuclear (CBRN) Regiment and NATO's Rapid Reaction CBRN Battalion.

The US-led coalition has taken serious note of ISIL chemical endeavours and targeted two of its chemical facilities near Mosul in March. According to De Bretton-Gordon, Kurdish security sources said that ISIL was also using the Mishraq chemical factory in southern Mosul as a centre for producing chemicals.

"They [ISIL] have a very high level of expertise but I doubt [that they have] the facilities to make anything but a small amount of chemical weapons," De Bretton-Gordon told Al Jazeera.

Iraq: Kurds increase pressure on ISIL near Mosul

Kurdish officials also tend to agree that, at least so far, ISIL doesn't have the means to build sophisticated chemical weapons with large scale impact. "They weaponise the chemicals by putting them into mortar shells or in some cases even cooking gas cylinders," says General Ali. "These shells are only effective if they land very close to the target, like a few metres."

However, the Australian Foreign Secretary Julie Bishop warned in June that ISIL might have among its recruits the "technical expertise necessary to further refine precursor materials and build chemical weapons."

With the battle of Mosul looming, the United States has donated more than 10,000 masks since last autumn to two Kurdish brigades trained for the Mosul operation, a coalition spokesman who spoke on condition of anonymity due to the sensitivity of the subject, told Al Jazeera.

This is the first major provision of such anti-chemical gear to the Kurdish forces, which perhaps indicates serious concerns that ISIL might launch chemical attacks on the forces advancing towards its largest stronghold in Iraq and Syria.

In the Sultan Abdullah hills, a couple of kilometres to the east of Jaralla where Chato Saeed was wounded, a chemically polluted room is a standing testament to ISIL's experimenting with deadly gasses. The area was targeted by ISIL last summer. Since then, only 40 gas masks have been provided to a battalion of 400 members at this outpost.

One fighter, who spoke on condition of anonymity because he was not authorised to speak to the press, expressed deep concern that he and many other fellow fighters along the sprawling 1,000km Kurdish-held frontline remain vulnerable to gas attacks.

For its part, ISIL has signalled that it will not have second thoughts about using such weapons. The group's latest chemical attack in northern Iraq occurred on July 22 in Tal Afar area west of Mosul and wounded three Kurdish Peshmerga fighters.