There are 3 main types of scent oils:
Perfume oils are blended from synthetic, natural and / or nature-identical oils. Its not called essential oil.
Nature-identical oils are synthetically but produced like the natural original. They may becomposed of different natural or nature-identical substances.
Pure essential oils are exclusively obtained from each plant by extraction.
Essential oil basically means that the oil - even at low temperatures - evaporates completely. Making candles with it has the problem that the oil must "survive" the melting temperature. One should choose an extremely low wax temperature to keep the oil in the wax.
More "solid" are the perfume oils.
Adding between 0.1 and 5%, depending on the wax and the scent has to be tested. Too much fragrance oil causes opacities in gel wax or “bleeding” in paraffin and other hard waxes. Some oil varieties can make gel wax cloudy even with small quantities.
The fragrance oils of the http://www.kerzenkiste.de are highly concentrated and undiluted.
Because of this, they must be identified in accordance with the Hazardous Substances Regulations. (Irritant, Dangerous for the environment, etc.). This only applies to the substance in concentrated form. Scented candles with an oil content of less than 10% are not covered by the Regulation.
Last but not least: Please handle all fragrance oils - even the finest, all-natural fragrances - with care, if they are present in a concentrated form. When adding to liquid wax, large quantities of the oil evaporate. This oil foam does not belong into the lung. Please always work with full ventilation. If that is not possible, it is safer to wear protective masks..