Air Filters, Duct Cleaning and Ozone Devices

Frequently Asked Questions

Do I need an air cleaner, what kind should I buy?

Are air cleaners that use ozone safe and effective?

Does cleaning the ductwork in the home reduce indoor air contamination?

Is vacuuming an effective way to remove biological contaminants that have settled onto surfaces?

Question: Do I need an air cleaner, what kind should I buy?

The United States Environmental Protection Agency (USEPA) has researched the issue of air filters and duct cleaning in their publication Residential Air-Cleaning Devices: A Summary of Available Information. The following is an excerpt from that document:

"Some air filters, under the right conditions, can effectively remove small particles which are suspended in air. However, controversy exists as to the efficacy of air filters in removing larger particles such as pollen and house dust allergens, which rapidly settle from indoor air. In assessing the ability of an air cleaner in removing allergens, one should consider the relative contribution of airborne to surface concentrations of the allergens, particularly in the case of pollen and house dust allergens where natural settling may be so rapid that air cleaners contribute little additional effect. Animal dander may settle more slowly, although, again, the surface reservoir far exceeds the amount in the air. Furthermore, control of the sources of allergens and, where allergens do not originate outdoors, ventilation should be stressed as the primary means of reducing allergic reactions."

To paraphrase the above excerpt in layman’s terms, some allergens are small and can float in the air for a long time while others are large and rapidly fall to the floor or other surface (like furniture). Air filters, as the name implies, can only remove the allergens if they are suspended in air (floaters). If the allergen you are reacting to is a “floater”, an air filter may be able to remove it and alleviate your symptoms. If it is a “sinker,” the allergen will probably not be in the air long enough for the air filter to “catch” it so its use is unlikely to have a significant beneficial effect. The most effective way to solve your problem is to prevent allergens from getting into your house and if that is not possible, provide adequate ventilation (aka “fresh air”) to dilute their concentration.

The USEPA recommends consumers refer to either of these publications before purchasing a device:

• Residential Air-Cleaning Devices: A Summary of Available Information, from EPA
• Air Cleaners, from Rutgers Cooperative Extension

Go Back to the top of this page

Question: Are air cleaners that use ozone safe and effective?

The use of ozone devices is a controversial issue and the Volusia County Health Department does not recommend their daily use in typical residential situations. An excellent discussion of this issue can be found in the EPA document, Ozone Generators that are Sold as Air Cleaners. The following discussion is an excerpt from this document:

Ozone generators that are sold as air cleaners intentionally produce the gas ozone. Contrary to the claims of some vendors, no agency of the federal government has approved these devices for use in occupied spaces. In fact, when ozone is inhaled, it can damage the lungs. Relatively low amounts can cause chest pain, coughing, nausea, throat irritation, and congestion. It may also worsen bronchitis, heart disease, emphysema, and asthma, and can compromise the ability of the body to fight respiratory infections.

Although manufacturers and vendors of ozone generators may describe ozone as "energized oxygen" or "pure air," ozone is a toxic gas with different properties from oxygen. In fact, several federal agencies have established health standards or recommendations to limit human exposure to ozone. Scientific studies have shown that when ozone concentrations do not exceed these public health standards, ozone has little potential to remove indoor air contaminants. Particles such as dust and pollen that cause allergies are not removed by ozone. Ozone is also not effective at removing many odor-causing chemicals, nor does it remove viruses, bacteria, mold, or other biological pollutants. Some studies show that ozone concentrations produced by ozone generators can exceed health standards even when the manufacturer's instructions are followed.

High concentrations of ozone are sometimes used to help decontaminate unoccupied spaces from certain chemical or biological contaminants or odors, but these should only be used when people are not present.At these high concentrations, ozone can be toxic to human health and adversely affect indoor plants, and damage materials such as rubber, electrical wire coatings, and fabrics and art work containing susceptible dyes and pigments.

The public is advised to use proven methods of controlling indoor air pollution such as: eliminating or controlling pollutant sources, increasing outdoor air ventilation, and using safe, effective methods of air cleaning.

Question: Does cleaning the ductwork in the home reduce indoor air contamination?

Why do you want to clean your ducts? If they are “dirty” and you want to remove the debris, duct cleaning may be appropriate. If your goal is to use duct cleaning to solve an indoor air-related health problem, duct cleaning is unlikely to be effective. An excellent discussion of this issue can be found in the EPA document, Should You Have the Ducts In Your Home Cleaned? The following discussion is an excerpt from this document:

"Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts. This is because much of the dirt in air ducts adheres to duct surfaces and does not necessarily enter the living space.

It is important to keep in mind that dirty air ducts are only one of many possible sources of particles that are present in homes. Pollutants that enter the home both from outdoor and indoor activities such as cooking, cleaning, smoking, or just moving around, can cause greater exposure to contaminants than dirty air ducts. There is no evidence that a light amount of household dust or other particulate matter in air ducts poses any risk to your health.

Air duct cleaning may be indicated in gross contamination situations such as:

• Substantial visible mold growth present in hard surface (e.g. sheet metal) ducts or on other components of your heating and cooling system
• Ducts are infested with vermin (e.g. rodents or insects)
• Ducts are clogged with excessive amounts of dust, tobacco ash and debris and/or particles are actually released into the home from your supply registers when used.

Go Back to the top of this page

Question: Is vacuuming an effective way to remove biological contaminants that have settled onto surfaces?

Vacuuming surfaces disturbs the particles on the surface and causes the smallest ones to become airborne. In perfectly still air, particles smaller than 20 microns in size (about one-half the diameter of the finest human hair) stay suspended in the air. If the air dischare from the vacuum is downward, it can disturb settled dirt particles and cause them to become airborne. Research has shown a 98 percent increase in household airborne dust in the two-hour period following vacuum cleaning when the cleaner discharges downward over a dirty carpet.

Using a cleaner that discharges upward can result in a 35 percent increase in dust in the air. This is because the surface contaminants become airborne through the filter. The vacuum cleaner filter bag retains only the larger particles and allows the smaller ones to pass into the room air.

Some vacuum cleaners are designed with high efficiency particulate air (HEPA) filters that remove at least 99.97 percent of the smallest particles in the discharge air. A central vacuum system with the motor, suction blower, and filter bag located in the basement or garage may solve the problems of portables because there is no air discharge in the room being vacuumed. The filter may also be much larger, allowing high efficiency filtration of the vacuum cleaner discharge air with enough air flow to suck embedded dirt off a carpet.

Back To Public Health | Contact Us | Subject Index |