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The Do's And Don't Of Particle Filters And The effect On The IT Space

Jun 13, 2013

What dust? I don’t see no stinking dust!



Dust Accumulation in a Dell Laptop (Source)


What particle filters do, what they don’t do, and how it affects filter selection for IT spaces.

Up to now, this series has discussed particle filtration in data centers. All IT spaces, including computer, telecom, server, and instrument rooms require particle filtration in their air handling systems for optimum performance.  But why is this so?

Earlier it was mentioned that when I personally replaced a standard hot air heating system filter with one rated to reduce allergens, the high efficiency filter removed a remarkable amount of dust in comparison to the standard one. Nothing in the house changed; the dust particles had been there all along.  They simply passed through the standard filter without slowing down.  Luckily, as my family doesn’t suffer from allergies, our health was not affected by the particles. Otherwise, for all intents and purposes, the furnace performed well with the standard filter.  However, this is not the case for CRAC units, where a little dust on the cooling coils can degrade efficiency.  Note to self: vacuum refrigerator coils, summer is arriving in two weeks.

Dust Accumulation in Laptop Fan (Source)

More importantly, dust on electrical components can insulate them and keep them from dissipating heat as designed.  This can overheat and stress components, leading to reduced or intermittent performance and in some cases, premature failure, especially toward the end of the device’s life. That’s why all of the IT equipment manufacturers specify particle filtration as a condition in their warranty language. Images on the web are more likely to show extreme examples in laptops and home computers, but the same can be seen in poorly maintained servers.

But what is this dust, and how does the filter keep it out? Dust is a buildup of fibers (natural and synthetic textiles, hair, fur, microscopic plastic, wood and metal scrapings from flooring, shoes, desks, etc.; plant, animal, soil, sand, pavement, building materials from the ambient environment, and the residues from combustion such as soot and smoke particles. Keep in mind, bacteria, mold spores, and viruses are particles in the air that can also be trapped in the filter. They can be visible or invisible, and are sometimes too small to see with even the most powerful of microscopes (viruses for example).  Here’s an example of the range of particles that may be found in the air at any given time.

Particle

Particle Size
(microns)

one inch (24.4 mm)

25400

dot (.)

615

Eye of a Needle

1230

Beach Sand

100 - 10000

Mist

70 - 350

Pollens

10 - 1000

Textile Fibers

10 - 1000

Human Hair

40 - 300

Dust Mites

100 - 300

Saw Dust

30 - 600

Mold Spores

10 - 30

Red Blood Cells

5 - 10

Spider web

2 - 3

Combustion-related - motor vehicles, wood burning, industrial processes

up to 2.5

Milled Flour, Milled Corn

1 - 100

Coal Dust

1 - 100

Talcum Dust

0.5 - 50

Copier Toner

0.5 - 15

Liquid Droplets

0.5 - 5

Anthrax

1 - 5

Smoldering or Flaming Cooking Oil

0.03 - 0.9

Bacteria

0.3 - 60

Combustion

0.01 - 0.1

Burning Wood

0.2 - 3

Tobacco Smoke

0.01 - 4

Viruses

0.005 - 0.3

Typical Atmospheric Dust

0.001 to 30

Carbon Dioxide

0.00065

Oxygen

0.0005

Table edited for length. (Source)

Different geographical locations have unique variables to consider, including the local environment (arid, tropical, arctic, etc.), local culture (cooking and heating methods, popular modes of transportation, hygiene practices, etc.), the site’s policies and practices in the selection of materials used and allowed in IT spaces, access practices (gowning, etc.), and HVAC system maintenance.  In clean rooms, such as those used for integrated circuit production at companies like Intel, Samsung and TSMC, the removal of particles is especially critical. The cleanliness requirements for microprocessors and flash memory devices are significantly higher than a server closet, as the finished chips must operate under their defined specifications without obstruction or minuscule imperfections. After assessing the particle loading potential in any given site, the cost of filtration, cleaning, and other measures can be weighed against the OEM’s requirements.

Typical Particles found in the Environment (Source)

Local HVAC service companies are very familiar with the particle filtration needs of their areas.  By matching this knowledge with the site’s policies and practices, one can easily determine the optimum particle filtration for any given location. From data closets, to server rooms, and even in microprocessor factories, staying informed on best practices in filtration is always a wise move. 

IC Wafer Lab (Source

 

If you have other suggestions, tips, or insights on this issue, feel free to chime in on the comments section of this page!



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