One nurse at the National Poison Emergency hospital, who declined to say her name, told AFP she had never seen the numbers of carbon monoxide poisoning patients so high.
“We are working under an enormous amount of pressure,” she says.
The city’s emergency unit said issues were easing once people were told the “correct ways to burn the briquettes”.
They said public service workers were spending time in the ger district to teach people about the new fuel as well as to report if any raw coal was still being used.
Its the latest example of governments in Asia struggling to find a safe, workable solution to replacing coal, in a region that is battling toxic levels of air pollution.
In India, Prime Minister Narendra Modi’s promise to provide cooking gas connections to millions of rural residents has been beset by corruption.
In neighbouring China, three million homes near Beijing were ordered to switch from coal to gas or electric heating in 2017, but a difficult transition left many without any heating at all.
Ulaanbaatar is the world’s coldest capital and only half of the residents have central heating, and Ulaanbaatar regularly exceeds World Health Organisation recommendations for air quality.
The government has been trying to force low grade coal out of commission to reduce the thick air pollution that has plagued the city.
And experts say there is evidence that the move is already having a positive impact on the environment.
Sonomdagva, associate professor at the National University of Mongolia, told AFP that PM 2.5 — tiny particles that get into the lungs and bloodstream — had decreased by 40 percent compared with October last year.
“However, an incredibly long and warm autumn, plus the usage of the new refined fuel, and fear of suffocation meaning people use only wood (for fuel) can also be reasons of the 40 percent decrease,” he said.