Airborne Pollutants

In order to remove airborne pollutants from your home, you must first educate yourself on which pollutants cause the most harm, and how these make their way inside to where they can affect you. Some of the most common, and most harmful are listed below:
· Environmental Tobacco Smoke (ETS), commonly referred to as Secondhand Smoke
· Mold, Bacteria, Animal Dander, Pollen
· Dust
· Combustion Products, such as Carbon Monoxide and Nitrogen Dioxide
· Cleaning Agents
· Beauty Products
· Hobby Products
Secondhand smoke has been proven to contribute to cancer, respiratory infections, and Asthma. According to the American Lung Association, "Secondhand smoke is responsible for between 150,000 and 300,000 lower respiratory tract infections in infants and children under 18 months of age, resulting in between 7,500 and 15,000 hospitalizations each year, and causes 1,900 to 2,700 sudden infant death syndrome (SIDS) deaths in the United States annually." 1
In recent years, action has been taken in some states to eliminate Secondhand Smoke in public buildings. For example, Delaware, New York, Massachusetts, and Rhode Island prohibit smoking in all private workplaces, restaurants, and bars. Connecticut, Vermont, and Maine prohibit smoking in all restaurants and bars. 2 However, this is not the case in all areas, and these smoking bans do not apply to private homes. If there are smokers in your home, this will affect everyone else in the household. It is strongly advisable to eliminate this source of indoor air pollution.
Biological air pollutants, such as mold, bacteria, animal dander, and pollen can also find their way into your home. Mold and mildew can grow in areas with too much moisture buildup. If rooms in your home have higher than 50% humidity, you are at risk. Animal dander is present in your home if you keep indoor pets, such as cats or dogs. The dander is created from the saliva these animals use to clean themselves. Indoor pets are also likely to shed, and airborne fur, hair, and related particles can cause allergic reactions in some people.
Combustion products, such as Carbon Monoxide and Nitrogen Dioxide are colorless and odorless, but pose a health risk if they are allowed to build up in the air. Carbon Monoxide and Nitrogen Dioxide are produced by any activity in the home that involves combustion, such as the use of a gas stove.
Any household cleaning agents, beauty products, or hobby products containing spray chemicals will wind up polluting your indoor air. The effect this has on what you breathe is intensified when these products are used in confined, inadequately ventilated areas in your home.
For more information on the potential pollutants that exist in your home, take the American Lung Association's Clean Air Assessment.

Air Devices Used in Hospital

An air cleaning device has been developed, with which a room in a general hospital ward can be converted into a biological clean room. Measurements inside the unit showed that the particle concentration (particle diameter .GEQ.0.5.MU.m) was reduced from 240,000/ft'3' to 100/ft'3' after operation. However, when an air conditioner was used simultaneously, it decreased to only 3,000/ft'3', so two layers of a medium efficiency particulate filter were installed over the exit of the air conditioner, which improved the particle concentration to 1,000/ft'3'. No airborne microbes were detected inside the unit. This result shows that the device is effective for the prevention of infection during the myelo-suppressive period of chemotherapy. A major advantage is that it can be easily installed without any construction.

Pollutant Destruction

Some air cleaners use ultraviolet (UV) light technology intended to destroy pollutants in indoor air. These air cleaners are called ultraviolet germicidal irradiation (UVGI) cleaners and photocatalytic oxidation (PCO) cleaners. Ozone generators that are sold as air cleaners intentionally produce ozone gas, a lung irritant, to destroy pollutants.
UVGI cleaners use ultraviolet radiation from UV lamps that may destroy biological pollutants such as viruses, bacteria, allergens, and molds that are airborne or growing on HVAC surfaces (e.g., found on cooling coils, drain pans, or ductwork). If used, they should be applied with, but not as a replacement for, filtration systems.
PCO cleaners use a UV lamp along with a substance, called a catalyst, that reacts with the light. They are intended to destroy gaseous pollutants by converting them into harmless products, but are not designed to remove particulate pollutants.
Ozone generators use UV light or an electrical discharge to intentionally produce ozone. Ozone is a lung irritant that can cause adverse health effects. At concentrations that do not exceed public health standards, ozone has little effect in removing most indoor air contaminants. Thus, ozone generators are not always safe and effective in controlling indoor air pollutants. Consumers should instead use methods proven to be both safe and effective to reduce pollutant concentrations, which include eliminating or controlling pollutant sources and increasing outdoor air ventilation.

Negative effects of air cleaning devices

Ozone production

Some air cleaners (called ozone generators) use an electrical charge to generate ozone. Although ozone (also referred to as trivalent oxygen or saturated oxygen) is a necessary part of the upper atmosphere (10-30 miles above us), in the part of the atmosphere we breathe, ozone is a potent lung irritant. It can have damaging health effects, especially for persons with asthma and other lung diseases, children and the elderly. It is produced directly by ozone generators and indirectly by ion generators and some other electronic air cleaners. This will be further discussed.

Diagrams

Figure 1.1 Shows an example of an electronic cleaning device

Mechanical filters

Mechanical filters used for air cleaning can actually be further classified into two major types.

1. Flat or panel filters generally consist either of a low packing density of coarse glass fibers, animal hair, vegetable fibers, or synthetic fibers often coated with a viscous substance (e.g., oil) to act as an adhesive for particulate material, or slit and expanded aluminum. (A flat filter in use in many homes is the typical furnace filter installed in central heating and/or air-conditioning systems.) Flat filters may efficiently collect large particles, but remove only a small percentage of respirable size particles.
   
   Flat filters may also be made of "electret" media, consisting of a permanently-charged plastic film or fiber. Particles in the air are attracted to the charged material.
   
2. Pleated or extended surface filters generally attain greater efficiency for capture of respirable size particles than flat filters. Their greater surface area allows the use of smaller fibers and an increase in packing density of the filter without a large drop in air flow rate.

Some newer systems on the market are referred to as "hybrid" devices. They contain two or more of the particle removal devices discussed below. For example, one or more types of mechanical filters may be combined with an electrostatic precipitator or an ion generator.