Mitigating Particulates Emitted by Mosquito Coils Using Unipolar Ionisers: Implications to Deposition in Human Respiratory Tract System

Abstract

Negative ion generators (NIGs) have been efficiently used for the reduction of airborne particulates in indoor environments. The mechanisms of particle removal include particle charging by emitted ions and electro-migration from air to wall surfaces. This study explores the dependence of size on particle removal from air in the presence of an ioniser. The test aerosols used were the combustion particulates generated using mosquito repellent coils that are very often used in urban homes in the Asian and African regions. In addition to the main component allethrin, organic fillers are added to these coils to aid smouldering. This could lead to a heavy airborne particulate loading over a very wide size range, all of which may not be beneficial. Room experiments showed that the particle concentration was reduced by a factor of about 15 for sizes of 40 nm and decreased to about 1.5 for 0.3 µm, thus leading to an increase in the median diameters in the presence of the ioniser. Implications to the deposition of these particles in the human respiratory tract system are discussed and there is a significant reduction in the deposition when the ioniser is operated.