Indoor Air Cartoon Journal, June 2019, Volume 2, #61

The amount of particle toxins that go into the human body, primarily through respiration, will be reduced if exposure to the indoor particle is reduced. The low dose of particles will reduce the adverse health effects associated with respiratory – see last week. With this understanding, the removal of particles, which may carry chemical or biological toxins, from indoor air is essential. Evidence in the literature suggested filtration as an energy-efficient strategy for increasing clean air delivery rate (CADR). CADR is the amount of clean air delivered to an indoor environment.

The material, the design, and condition of filter fibre – material that made up a filter – will determine its ability to remove particles from the air stream and the strength of the bond that holds particles to the fibre. Typical filter fibre uses interception, inertial impaction, and diffusion mechanisms to remove particles from the airstream. A filter fibre that is positively charged uses electrostatic attraction mechanism to attach particles that are negatively charged to itself and remove them from the airstream.

The higher the particle removal efficiency of filter fibres, the higher would be their CADR. The stronger the bond between particles and filter fibres, the longer the particles stay on the filter fibres and not resuspend to the airstream. Even if filter fibres can hold particles for a longer period, adequate maintenance of the filter and operation of the HVAC system are required to prevent odour associated with used filters. The efficiency of filter fibres to remove particles from the air and hold on to them for a more extended period with little or no odour discomfort will determine the appropriateness of the adopted filter for healthy indoor air. The concentration and type of particles and operation and maintenance required for the filter and HVAC system should determine the type of particle filters adopted.

Do you want to know more about this topic? Read Azimi and Stephens (2013), Sublett (2011), Waring et al. (2008), and Xu et al. (2010) papers.