A City Hall water truck sprays into the air to reduce the dust along Prachachuen Road in Bangkok on Tuesday. (Photo by Pornprom Satrabhaya)

The Bangkok Metropolitan Administration (BMA) has announced a plan to install a four-metre air purification tower in central Bangkok, in a pilot project to combat the PM2.5, or fine particulate matter, pollution blanketing the city.

Chatree Watanakhajorn, director of the BMA's environment department, said on Tuesday the first tower woud soon be placed near the Siam BTS station.

If the giant air purifier proves effective, more will be installed across Bangkok, he said.

A private firm and Kasetsart University jointly proposed the towers priced at 5.3 million baht each.

If the tower, which is about four metres tall and 1.5 metres wide and weighs about 200 kilogrammes, proves capable of reducing the haze pollution, the BMA will ask companies, department stores and organisers of large gatherings to place similar towers on their buildings.

According to Mr Chatree, the tower is capable of cleaning polluted air out to a radius of 1,000 metres.

Should a decision be made to install more towers, they would be erected in 24 busy areas - including Ratchaprasong intersection, Asok intersection, Central Department Store at Lat Phrao, Ari BTS station, Chatuchak, Chong Nonsi, Phrom Phong, Ploenchit and Victory Monument stations.

Mr Chatree said the BMA is also looking to buy six water spraying trucks to help reduce dust levels. City Hall is waiting for budget approval from the city council. If approved, specifications for the truck purchase will be drafted.

The trucks, which are capable of spraying water up to 10 metres into the air, are used in other countries affected by fine dust particles, such as China and India.

At 8am on Tuesday, Bang Phlat district recorded the highest PM2.5 dust haze level in the city, at 81 microgrammes per cubic metres of air, which is well above the 50 µg/m³ maximum so-called healthy level.

Bang Phlat is among the 24 districts the BMA monitors for air pollution. PM2.5 levels in the city ranged between 56 µg/m³ and 81 µg/m³ at 8am on Tuesday.

The BMA has advised people to avoid outdoor activities and wear face masks if they need to be outside for an extended period.