Digital strategist Ashik Ashokan and case worker Ashok Kumar.
In three years, they have climbed five volcanoes.
But it is their first volcanic ascent in Iran in 2015 that stands out because one of them suffered a fractured arm during a hurried descent.
Now more experienced, they will try to conquer their sixth volcano this month to raise funds for the Singapore Association of the Visually Handicapped (SAVH).
Digital strategist Ashik Ashokan and case worker Ashok Kumar, both 27, make up climbing duo Heart2Climb.
While they aim to raise funds for the SAVH, they have not set any targets and hope the public will respond generously.
The money will be used for the running of the association's day care programme, which has 60 elderly patients who are visually impaired.
The best friends discovered their passion for climbing by accident. They were in Nepal in May 2013, and on a whim decided to hike up Poon Hill, a 3,210m tall mountain.
They did not train for it, did not wear layers of protective clothing and filled their bags with unnecessary items such as canned fruit and stylish jackets, which were of little use in the cold.
They managed to make it to the summit after three days, although it was a miserable ascent because of the stormy weather and intense cold.
Mr Ashik said: "But surviving each and every one of those terrible experiences brought a sense of fulfilment."
Since then, they have also climbed volcanoes Mount Giluwe in Papua New Guinea and Mount Elbrus in Russia.
They will be leaving Singapore today for Chile, where they will be climbing Ojos del Salado to raise funds for the SAVH. It is located near the Atacama Desert, and at 6,893m is the highest active volcano in the world.
Last year, a mountaineer died attempting to climb Ojos del Salado.
Mr Ashik and Mr Ashok are aware of the risks involved, with their 2015 Iran experience still on their minds.
Out of excitement, they tried to descend Mount Damavand - which at 5,680m is the highest peak in Iran and one of the highest volcanoes in Asia - quickly.
They underestimated the risks and in their haste, Mr Ashik tripped and broke his right arm. He managed to walk down on his own.
The duo climbed for non-profit organisations SPD in 2014 and for the Children's Cancer Foundation in 2015.
Mr Ashok said: "Those with disabilities have to climb mountains in their everyday lives, and yet they are underrepresented in our society.
"We climb mountains to draw parallels to their struggles, and to raise public awareness about the difficulties they face."
For the current trip , the friends underwent a 60-day training regimen, carrying haversacks filled with mountaineering equipment such as ice picks and harnesses, and bags of rice.
They walked at least 20km in parks and climbed 17 storeys at least 10 times a session. Mr Ashik tried to train once a week.
On their Chile trip, Mr Ashok said: "I am motivated to do my best because the visually impaired wake up every day and face so many challenges throughout the course of their day, and yet they remain strong."
