Incense 1–6 were traditional incense used to worship
deities. In a regular HK family, three incense sticks
would be burned once per day on first or 15th day of
Chinese lunar and one incense stick would be burned
once per day on non-first or non-15th day of Chinese
lunar. Three traditional incense sticks were burned
simultaneously duringeach experiment. Amongthese,
Incense 2 and 6 were claimed to be environmentalfriendly
incense, which was expected to cause less air
pollution problems. While, Incense 7–9 were aromatic
incenses which were claimed to have aromatherapy use.
The common practice was burningone stick each time.
On this ground, one stick each of Incense 7–9 was
burned in each set of experiment. Incense 10 was church
incense burned in a charcoal thurible.