In the lead-up to the Beijing Olympics, security is tight at all entry and exit points in China.

Hongqiao and Pudong are the two airports serving Shanghai. In addition to normal check-in procedures, luggage and hand-carry items will also be checked at entrances to terminal buildings.

Lu Jian Hua, vice-president of Shanghai International Airport Co. Ltd, Security Services, said: "When passengers enter the terminal building, we take a sample of their bags and analyse them using a special device. If we detect any explosive substances, the alarm will go off in 5 to 6 seconds. We will then check their bags again."

Security workers would use chemical paper to rub on the luggage. The paper is then scanned by machines which will be able to detect explosive, flammable, biochemical or radioactive material.

The new practice came into effect on July 20 across 18 cities and regions around China, including Beijing. Due to the extra security, authorities are advising passengers to arrive earlier than usual to avoid missing their flights.

Some passengers were prepared for potential delays, while others were unaware of the stepped-up security measures.

Airport officials said these measures are in place to ensure everything runs smoothly.

"We have opened 27 check lanes and four one-way exits in both terminal buildings. Passengers won't be affected too much when entering the terminal building," said Lu.

Authorities said the measures will be in force for two months, but could be extended because China is celebrating its national day on October 1.

Shanghai will play host to 12 soccer games during the Olympics in August.