For a candle to burn, it requires a spark, which provides the activation energy for the oxidation reaction of the hydrocarbon making the candle.
It also requires oxygen to facilitate the oxidation of the hydrocarbon.
Therefore the two main requirements of combustion of a candle are oxygen and a spark (or an initial flame)
Radiation is s very powerful substance and can cause major health problems do the health care professionals limit the use to help not create sickness
71% of the earth is water and the 29% is continents and islands.