Ultrafine Particles

What are Ultrafine Particles?
Ultrafine particles are airborne particles that can cause personal discomfort and health reactions when inhaled by the occupants of a home. The term "ultrafine particles" refers to particles that cannot be seen by the naked eye, and are smaller than 30 microns. To give an idea of size of 30 microns, it takes 25,000 microns to make one inch, and the very finest human hair is about 30 microns in diameter.  About 99% of the particles suspended in indoor air are too small to see. One cubic foot of air may contain as much as 400 million unseen particles, the majority of which will be much smaller than 30 microns. 

Health Effects of Ultrafine Particle Exposure
The specific health effects of ultrafine particles are not well understood.  They may affect health by their sheer volume, and/or chemical makeup. Current evidence shows that ultrafine particles can trigger immune system reactions in susceptible individuals, but many scientific and medical professionals suspect that ultrafine particles may also contribute to asthmatic or allergy like symptoms.  Scientific and medical communities in association with regulatory agencies believe the link between ultrafine particles and human health is one of significance.

Types of Ultrafine Particles
Ultrafine particles can come from many sources, including but not limited to:
Chemical: usually the products of combustion or chemical reactions occurring at a wide variety of sources. 
Dust: Can enter your home through normal air infiltration or by being tracked into the home then ground up by repeated foot traffic until it is of small enough size to stay suspended in the air. Some dust is generated from other products such as asbestos which can be as small as 0.3 microns. 
Pollen, mold and plant/mold spores: Also may enter the house from outside air or may be generated inside the home in high humidity areas including bathrooms and crawlspaces.
Viruses and Bacteria: May be present inside your home under normal conditions. Viruses (.003 to .05 microns) are much smaller  than bacteria (.3 to 30 microns) but both will "piggyback" on larger particles of dust. 
Lint: Encompasses carpet and clothing fibers, as well as cat, dog, and human hair.
Combustion Contaminants & Smoke: These ultrafine particles are produced by smoking, burning candles, cooking, and from the biggest producer, combustion appliances. Smoke particles entering your home through stoves, chimneys, and vents are not always visible to the naked eye.

Will Air Filters Reduce Ultrafine Particles?

Air cleaning is one of three methods of reducing contaminants in indoor air.  Removal of the source or control of its emissions is the first step to cleaning the air. Proper ventilation is the next step.  While it is almost impossible to control the emissions of ultrafine particles, the maintenance of combustion appliances, cleaning dusty surfaces, and providing adequate ventilation to the house will help.   An air cleaner will work well in conjunction with these other steps, however, air cleaning alone cannot adequately remove all ultrafine particles.  There are a variety of filters available though the particles they capture are 0.3 microns and larger. 

Air Filters Effectiveness
The smallest particles captured by filters are 0.3 microns. Particles smaller than 0.3 microns are, some dust, viruses, some wood and tobacco smoke. An electronic air cleaner has 75% efficiency at 0.3 microns, and 100% efficiency at 30 microns.  Pleated media filters have a 35% efficiency at 0.3 microns and a 97% efficiency at 30 microns.  In stark contrast, furnace filters have only a 2% efficiency at 0.3 microns and only a 70% efficiency at 30 microns.  In general the smaller the particle, the less effective the filter, therefore an air filter will never be 100% effective at removing ultra fine particles.

Ultra Fine Particle Sizing
These are some common household ultra fine particles:
Type of particle                         size in microns
Animal Dander                                .5 to 10
Bacteria                                         .3 to 30
Viruses                                        .003 to .05
Pollen                                          7 to 100
Plant Spores                                9 to 100
Suspended household dust            .001 to 20
Cooking oil smoke                        .03 to 30
Tobacco smoke                        .01 to  1
Wood smoke                                .07 to 3
Asbestos dust                                .3 to 10
Lung damaging dust                        .5 to 5
Human hair                                30 to 100

Testing for Ultra Fine Particles
Using the most advanced equipment available in the industry today, we at Wisdom & Associates, Inc. are using an ultra fine particle counter which measures ultra fine particles from 0.01 microns to 1.0 microns in diameter.  Traditional particle counting equipment will only measure from 0.5 microns to 10 microns.  This advanced equipment allows us to track ultra fine particles to the source.