3.2. Carbonyl compounds
Fig. 2 presents the concentrations of eight carbonyl
compounds measured for the ten types of incense during
and after incense combustion. The burningconcentration
levels of formaldehyde, butyraldehyde and valeraldehyde
were observed to be higher than after-burning
levels. However, the levels of acetaldehyde, acetone,
propionaldehyde and methacrolein reach the peaks after
the incense was extinguished. The 8-h average formaldehyde
concentration recommended by HKIAQO is
100 mgm3. The result shows that the formaldehyde
concentrations of six types of incense were higher than
the HKIAQO. Nevertheless, the formaldehyde concentrations
of Incense 3 both duringand after burningwere
substantially higher than the standard value; the burning
level exceeded the standard by 2 times. Ho and Yu
(2002) found that the formaldehyde levels in both the
temple yard and the home surpassed the WHO guideline.
This implies that the indoor incense-burning
environment adversely affects human health.