The frequency counted will be used to calculate the frecuency points and the air quality score of each area. The
tolerance group will give a (-1) for each frequency of lichen in the quadrant. If in the investigated square only the
tolerance group found, double the minus score if otherwise there is no need to double the score. The moderate
lichens will give a score of (+1) for each frequency in one quadrant. For the sensitive lichens, the frequency of the
lichen at each quadrant will be multiplied by 2. The air quality score on each tree is equivalent to the average of the
total score of the frequency of the selected tree from 4 directions, i.e. north, south, east and west. The air quality
score for one area is the average for the total air quality score of all the trees in the specific area. The air quality
score of UKM is the average for the total air quality score for all the 27 areas studied.