12 mist cannon trucks disinfects a street of Wuhan, Central China's Hubei province, Feb 5, 2020.

Spraying disinfectant over an area is not recommended as long as the place is less affected by the novel coronavirus.

The 12 mist cannon trucks, with each weighing 12 tonnes, have arrived in Wuhan, noting that by adding disinfectant into the water, the trucks can be used as large disinfection equipment during the Covid-19 (coronavirus) pandemic.

Wuhan, the epicenter of the epidemic, has been disinfected to kill the virus during the peak of the disease in mid-February.

The move is not applicable to other less affected areas because the virus can hardly be transmitted through the open air. Instead, it is mainly transmitted via droplets discharged in close contact and is not able to keep alive for long while in the air.

According to a guidance issued by the Chinese Center for Disease Control, disinfection of the open air is listed as one of the improper measures.

It may backfire by polluting the air, earth, plants, underground water and even human body. Personal prevention measures are more effective than disinfecting the air.