It is known the environmental harm of using an earthenware stove with coal, but it remains a habit for many Vietnamese. Many families in both rural and urban areas in the North Viet Nam use them to overcome the rising costs of gas and electricity. A recent survey revealed that Hanoi Capital has about 55,000 beehive coal stoves, which burn a total of more than 528 tons of coal each day, filling the air with carbon dioxide. According to experts, the use of beehive coal poses serious threats to health. They normally produce carbon dioxide, but in unventilated rooms, they start to produce deadly carbon monoxide, which is a killer.