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Mr Albert Lam, Director-General of Civil Aviation today (May 10) said that the entire passenger fleets of the two Hong Kong based airlines are equipped with very efficient HEPA (High Efficiency Particulate Arrester) filters to remove viruses, and that aircraft itself is not a high risk environment for virus transmission.
"The HEPA filters, which are made of micro glass fibers, are 99.97 per cent efficient in removing dust and airborne contaminants with a particle size of 0.3 micron and above, including viruses. Size of droplet is larger than five microns. Depending on aircraft types, there are two to eight such filters installed in every aircraft. This is the same type of filter used by hospital operating theatres," Mr Lam said when explaining the operation of the inflight air circulation and filtration systems.
The World Health Organisation (WHO) agrees that the filter systems in commercial aircraft have proven to be effective against infectious disease.
"In flight, fresh air is introduced into the cabin continuously, and this fresh air is mixed with cabin air, which is passed through filters in about 50:50 proportion. The entire cabin air volume is exchanged every two to three minutes.
"The average relative humidity in the cabin is 15 to 20 per cent during flight. A low humidity environment has been shown to inhibit fungal and bacterial growth.
"Moreover, air supplied to aircraft toilets and galleys is not re-circulated but is expelled from the aircraft, and air in the cabin is drawn down and extracted at floor level," Mr Lam added, pointing out that there is no longitudinal flow of air through the cabin. The air supplied to one seat row leaves at approximately the same seat row, thus minimising airflow in the fore and aft directions. In other words, the air of one person passes another at floor level only.
Since mid-April, temperature checks for all arriving, departing and transit passengers at the Hong Kong International Airport have been implemented. In line with the WHO guidelines, Hong Kong carriers will not accept passengers with symptoms and signs compatible with Severe Acute Respiratory Syndrome (SARS). Local air operators also carry out scheduled cabin cleaning with cleansing agents accepted for use on aircraft. Air travel is not a high-risk activity, neither is aircraft itself a high-risk environment for SARS transmission," Mr Lam reiterated.
Meanwhile, the International Civil Aviation Organization (ICAO) published guidelines in early May for its Member States to help stop the international spread of SARS by air. It urges Contracting States to implement pre-boarding medical screening of passengers at check-in; provide all incoming passengers with a detailed information leaflet on SARS; implement medical screening of passengers arriving directly from or via affected areas; advise pilots to radio ahead if someone on board exhibits SARS symptoms; instruct crew on dealing with suspected SARS-patients in flight; and disinfect aircraft on which a suspected SARS patient has travelled.
Hong Kong has already taken the necessary measures urged by ICAO to prevent the spread of SARS by air transport," Mr Lam said.
End/Saturday, May 10, 2003
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