Why does fire flame go up?

The flame heats any surrounding fuel so it releases gases as well. All the hot gases in the flame are much hotter (and less dense) than the surrounding air, so they move upward toward lower pressure. This is why fire typically spreads upward, and it's also why flames are always "pointed" at the top.

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And another question, why should you not burn candles for more than 4 hours?

If you burn your candle for more than 4 hours at a time, carbon will collect on the wick, and your wick will begin to "mushroom." This can cause the wick to become unstable, the flame to get too large, your candle to smoke, and soot to be released into the air and around your candle container. Regarding this, do candles really eat smoke? Removing the smell of smoke can be a difficult job involving time, effort, and money. Burning scented candles and perfumed aerosols are often used to remove smoke odor from a house. Ventilation can help to remove some of the smell, but it actually only dilutes the odor and does not remove the smell permanently.

Regarding this, is burning a candle for an hour the same as smoking?

He said it takes only an hour of burning a candle to produce the same effects as smoking a single cigarette. On top of that, research by the U.S. Environmental Protection Agency shows candles release the dirtiest soot, sometimes containing particles of zinc, tin and lead. Subsequently, can candles cause coughing? But while candles smell nice, about one in five people report reacting to candles with symptoms that include sneezing, a runny or stuffed-up nose, itchy eyes, sinus problems, head pain, hives or other skin rashes, coughing or wheezing.

One may also ask what are the healthiest candles to burn?

Beeswax candles are the healthiest choice in candles. Made from the caps of bee honeycombs, beeswax candles burn clean, are very long-burning, and give off a pleasant natural fragrance as they burn. Beeswax candles are dripless when burned properly, and release negative ions which help clean the air in a room.