Shanghai will test civil defense sirens across nearly the entire city on September 20, authorities said yesterday.

Only two areas - around the Pudong International Airport and Hongqiao Airport - will not be covered when the sirens sound between 10am and 10:23am.

The goal of the test is educational.

"We expect citizens to understand the different alarms and be able to react in case of an actual air attack," said Liu Nanshan, director of the Shanghai Civil Defense Office.

Three signals - a pre-alarm, air-raid alarm and all-clear siren - will be sounded one after the other at 10am, 10:10am and 10:20am, each lasting three minutes. The separate alarms signify that an attack is on the way, that an attack has begun and that danger has passed.

"The drill is meant to enhance citizens' sense of national defense," Liu said.

The first such drill took place in Jiading District west of the city center in 2000, and the alarm scale expanded to nearly the entire city for the first time this year.

Evacuation and rescue drills will be conducted in a few communities and schools this year, also growing larger in scale.

The civil defense office is considering possible nighttime tests in the future.

The air attack alarms may be used to warn of other disasters after citizens become familiar with the signals, Liu said.

In Hangzhou, Zhejiang Province, authorities decided to adapt the air attack alarm system to warn people about the dangerous annual tides.

(Shanghai Daily September 10, 2008)