20. Why is it dangerous to burn charcoal in rooms?
Because, being composed of carbon that is nearly pure, its combustion gives off a large amount of carbonic acid gas.
21. What is the effect of carbonic acid gas upon the human system?
It induces drowsiness and stupor, which, if not relieved by ventilation, would speedily cause death.
22. What is the reason that people feel drowsy in crowded rooms?
Because the large amount of carbonic acid gas given off with the breaths of the people, makes the air poisonous and oppressive.
23. What other causes of drowsiness are there?
The candles, gas, or fires that may be burning in the rooms where people are assembled. Three candles produce as much carbonic acid gas as one human being; and it is probable that one gas-light produces as much carbonic acid gas as two persons.
24. Have people ever been poisoned by their own breaths?
In the reign of George the Second, the Rajah of Bengal took some English prisoners in Calcutta, and put 146 of them into a place which was called the "Black Hole." This place was only 18 feet square by 16 feet high, and ventilation was provided for only by two small grated windows. One hundred and twenty-three of the prisoners died in the night, and most of the survivors were afterwards carried off by putrid fevers. Many other instances have occurred, but this one is the most remarkable.