1. PM-2.5 PARTICULATE MATTER : PM means Particulate matter, used for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.
  2. Particles less than 2.5 micrometers in diameter (PM2.5) are referred to as “fine” particles and pose greatest health risks.
  3. All types of combustion activities (motor vehicles, power plants, wood burning, etc.) and certain industrial processes are the main source for PM 2.5, particulate.
  4. Because of their small size (approximately 1/30th the average width of a human hair), fine particles can lodge deeply into the lungs.
  5. Indoor PM2.5 is composed of indoor-generated PM2.5 from sources such as smoking, cooking, and cleaning, and PM2.5 that has infiltrated from the outside.
  6. Two types of air cleaning devices can remove particles from the air — mechanical air filters and electronic air cleaners.
  7. Mechanical air filters

    remove particles by capturing them on filter materials. High efficiency particulate air (HEPA) filters are in this category.

  8. Electronic air cleaners

    such as electrostatic precipitators use a process called electrostatic attraction to trap charged particles. They draw air through an ionization section where particles obtain an electrical charge.

The charged particles then accumulate on a series of flat plates called a collector that is oppositely charged. Ion generators, or ionizers, disperse charged ions into the air, similar to the electronic air cleaners but without a collector. These ions attach to airborne particles, giving them a charge so that they attach to nearby surfaces such as walls or furniture, or attach to one another and settle faster.