You are here

API calculation

19 January, 2016 - 16:37

A network of air monitoring stations has been established in Hong Kong (the stations are shown in Figure 1.3) and real-time air quality data taken from each monitoring station are transmitted via telephone lines to the air quality data processing centre in the EPD office for the calculation of API.

Figure 1.3 The Hong Kong air quality monitoring network
 
Table 1.7 API sub-index levels & their corresponding concentrations
API sub-index level Relationship with HKAQO Corresponding concentrations (µg/m3)
RSP 24-hr SO2 24-hr SO2 1-hr NO2 24-hr NO2 1-hr CO 8-hr CO 1-hr O3 1-hr
0 - 0 0 0 0 0 0 0 0
25 50% Annual HKAQO / 25% HKAQO 28 40 200 40 75 2500 7500 60
50 Annual HKAQO / 50% HKAQO 55 80 400 80 150 5000 15000 120
100 HKAQO 180 350 800 150 300 10000 30000 240
200 - 350 800 1600 280 1130 17000 60000 400
300 - 420 1600 2400 565 2260 34000 90000 800
400 - 500 2100 3200 750 3000 46000 120000 1000
500 - 600 2620 4000 940 3750 57000 150000 1200
 

To view readings of the API for the last 24 hours, click here.