Answer
Since the room was not properly ventilated the gas-powered heater would have consumed all the oxygen in the air then due to lack of oxygen the fuel of the heater will not be able to burn completely and convert to carbon dioxide, instead it will incompletely burn to form carbon monoxide which is very dangerous. The carbon monoxide binds with hemoglobin in the blood and blocks the space for oxygen. Our lungs can only detect carbon dioxide not carbon monoxide so a person does not notice it and slowly suffocated due to lack of oxygen.
Work Step by Step
Same as above.
