NAFA Guide To Air Filtration Fourth Edition Chapter

NAFA Guide To Air Filtration Fourth Edition Chapter 1 Importance of Air Filtration presented by the National Air Filtration Association 2008

The Importance of Air Filtration. Air filtration supplies the means to obtain the level of particulate cleanliness required by any definition of “air conditioning. ” An air filter (air cleaner) is a device used for the removal of particulate or gaseous (molecular) impurities from the air.

Comfort Air Conditioning § Is described as the process of treating air to control simultaneously its temperature, humidity, cleanliness, and distribution to meet the requirements of the occupants of the conditioned space.

Air We Breathe

Aerosol - Gas § Regardless of its source, an airborne contaminant can be either an aerosol or a gas. § An aerosol is a suspension of solid or liquid particles in the air.

Measurement of Contaminants is in Micrometers aka Microns

1 MICROMETER A Micrometer (µm) is 1 millionth of a meter or in I/P - 1/25, 400 of an inch Pollen 10 to 100 micrometers Salt is 40 to 200 micrometers

Aerosols You’ve probably been asked by your friends, “Will I have to dust less if I buy one of your higher efficiency filters?

Particle Settling Velocities Particle Size (µm) 100. 0 50. 0 10. 0 5. 0 1. 0. 05 0. 1 <0. 1 Settling Velocity 59. 2 feet per minute 14. 8 feet per minute 7. 1 inches per minute 2. 5 inches per minute 5. 1 inches per hour 1. 4 inches per day 1. 13 inches per day negligible-behave like gases

Aerosols § Fumes are solid aerosols formed by the condensation of vapors of solid materials. § Fogs are liquid aerosols formed by the condensation of water vapor in the air. § Mists are liquid aerosols formed by the atomization of liquids. § Smokes are solid or liquid aerosols formed by the incomplete combustion of organic substances.

Gases § A gas is any material that has the tendency to expand indefinitely and which completely and uniformly fills the container it occupies. § Vapors are gases formed by evaporation of materials that are normally liquid or solid.

Measuring Particle Contamination § Measured by Weight – drawing air onto a pre-weighed paper target § Counting & Sizing – either through a membrane filter (old) or using an optical particle counter (OPC). See Chart on page 1. 4 – NAFA Guide

Size Distribution of Atmospheric Dust Sample 30 micron 10 micron Percent by Particle Count 0. 005% Percent by Weight 28% 5. 0 micron 0. 175% 52% 3. 0 micron 0. 25% 11% 1. 0 micron <1. 0 micron 1. 07% 6% 98. 5% 3% Source: NAFA Guide to Air Filtration

The Importance of Air Filtration. Air filtration supplies the means to obtain the level of particulate cleanliness required by any definition of “air conditioning. ”

Air Filters are used for a variety of purposes: § § § Protecting the health and well-being of the occupants of the space by removal of airborne microorganisms and particles. Protecting the décor of occupied spaces by removing the staining portion of airborne dust. Reducing maintenance of building interiors by reducing the frequency of washing such items as Venetian blinds and fluorescent bulbs.

§ § § Protecting the contents of occupied spaces including paintings, tapestries, and other items of historic or cultural value. Elimination of fire hazards by removing lint and other materials which might accumulate in the ductwork. Removing airborne bacteria from operating room air to help prevent postoperative infection.

Filter Efficiency § Properly evaluate the size of the particulate you want to remove. And at what efficiency. § Details on filter testing will be given in the presentation on Chapter 7. § ANSI/ASHRAE 52. 2 Method of Test

Filter 2 Filter 1 Draw-through System Detail

Blow-through System Possible Terminal Filter

Some Sample Questions 1 Millionth of a Meter is called a _____? Micrometer or Micron The air we breathe is composed mainly of _____? Nitrogen

Sample Questions The size of particles in outdoor air are mainly ? ? ? % and smaller? 1 Micrometer and smaller _____(size) particles behave like a gas, have negligible settling rates and are affected by Brownian Motion. Particles less than 0. 1 micrometers

Thank you. Other Questions?