The three are two women aged 68 and 26, and a seven-year-old boy. They are all residents in northern Lai Chau Province and currently stay in a rented house in Hanoi.

Illustrative image.

On Sunday evening, they burned the honeycomb charcoal for heating, setting the stove in a room and closing the door.

The boy started having headaches and nausea first before the two women experienced the same symptoms.

All three were then taken to Bach Mai Hospital in Hanoi for emergency aid.

They were diagnosed with carbon monoxide (CO) poisoning.

By Tuesday, their conditions had stablized, according to the hospital.

Doctor Nguyen Trung Nguyen, director of the Poison Control Center under the hospital said when heating or cooking in an enclosed space, oxygen will gradually be consumed. The combustion reaction in the absence of oxygen will form more and more CO gas.

CO has no smell and color and is very difficult to detect. When someone inhales it, CO quickly penetrates the blood and reduces oxygen levels in the blood, causing that person headaches, dizziness, nausea, chest pain, and confusion.

People who inhale large amounts of CO can pass out and die very quickly, especially pregnant women, young children, the elderly with chronic heart disease and lung disease, he said.

The doctor added as 40 percent of people with CO asphyxia will experience sequelae like memory loss, decreased concentration, facial muscle paralysis, abnormal movement, difficulty walking, stiff limbs and tremors, hemiplegia.

Since Feb. 18 a mass of cold air combined with rains has brought the coldest spell this winter. Temperatures in some places dropped below zero, causing snow to cover the trees and ground.

At 6 a.m. Tuesday all 25 northern localities recorded temperatures of below 10 degrees Celsius, according to the National Center for Hydro-Meteorological Forecasting (NCHMF).

The NCHMF said the cold spell could last until Feb. 24. It added north and north-central regions would experience temperatures of 8-11 degrees in the plains and zero to six in the mountains on Wednesday.

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Source: VnExpress