Pollution sources
Things that release gases or particles into the air are the primary cause of indoor air quality problems in homes. Inadequate ventilation can increase indoor pollutant levels because you are not bringing in enough outdoor air to dilute emissions from indoor sources - and because the indoor air pollutants aren't allowed to escape from your home. The EPA indicates high temperature and humidity levels can also increase concentrations of some pollutants.

According to the EPA, there are many sources of indoor air pollution in any home. (And there is no mention of Fido.) These sources include things that burn, such as oil, gas, kerosene, coal, wood and tobacco products; building materials and furnishings from deteriorated, asbestos-containing insulation, to wet or damp carpet, to cabinets or furniture made of some pressed wood products; products for household cleaning and maintenance, personal care or hobbies; central heating and cooling systems and humidification devices; and outdoor sources such as radon, pesticides and good-old outdoor air pollution.

Costanzo said the paint fumes and emissions from the finish of new furniture can be a source of pollutants, as can dirty carpet. "When the carpeting gets dirty, people walk on it and stir the dirt back up into the air," he said.

It's no surprise that the importance of any single pollution source depends on how much of a given pollutant it emits and how hazardous those emissions are. In some cases, factors such as how old the source is and whether it is properly maintained are significant. For example, the EPA notes an improperly adjusted gas stove can emit significantly more carbon monoxide than one that is properly adjusted.

The organization further explains that some sources, such as building materials, furnishings and household products, such as air fresheners, release pollutants more or less continuously. (Bet you never considered that flowery emission from your air freshener as "pollution.")

Other sources release pollutants intermittently. These include Grandma smoking, the use of unvented or malfunctioning stoves, furnaces, or space heaters, the use of solvents in cleaning and hobby activities, the use of paint strippers in redecorating activities, and the use of cleaning products and pesticides in house-keeping.

It all sort of makes you want to hold your breath - and the EPA notes these high pollutant concentrations can remain in the air for long periods after some of these activities.

Ventilation
Because our homes are so well-sealed-up to save energy on heating and cooling, at times too little outdoor air enters and pollutants can accumulate to levels that can pose health and comfort problems. Outdoor air circulates into and out of a home through infiltration, natural ventilation, and mechanical ventilation.

The EPA describes infiltration as when outdoor air flows into the house through openings, joints and cracks in walls, floors and ceilings, and around windows and doors. In natural ventilation, air moves through opened windows and doors.

"With today's homes being so tight to conform to the new energy standards, everything gets trapped inside," Costanzo said. "Open the windows on nice days to get a good air exchange."

Finally, there are a number of mechanical ventilation devices, from outdoor-vented fans that intermittently remove air from a single room, such as bathrooms and kitchen, to air handling systems that use fans and duct work to continuously remove indoor air and distribute filtered and conditioned outdoor air to strategic points throughout the house. (Yeah, we've all got this, right?)

Pollution and health
The EPA points out that health effects from indoor air pollutants may be experienced soon after exposure or, possibly, years later.

Immediate effects may show up after a single exposure or repeated exposures. These include irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. Such immediate effects are usually short-term and treatable. Sometimes the treatment is simply eliminating the person's exposure to the source of the pollution, if it can be identified. The EPA indicates that symptoms of some diseases, including asthma, hypersensitivity pneumonitis and "humidifier fever," may also show up soon after exposure to some indoor air pollutants.

Certain immediate effects are similar to those from colds or other viral diseases, the EPA says, so it is often difficult to determine if the symptoms are a result of exposure to indoor air pollution. For this reason, it is important to pay attention to the time and place symptoms occur. If the symptoms fade or go away when a person is away from home, for example, an effort should be made to identify indoor air sources that may be possible causes.

The long-term effects may show up either years after exposure has occurred or only after long or repeated periods of exposure. The EPA says that these effects, which include some respiratory diseases, heart disease and cancer, can be severely debilitating or fatal.

It only makes sense then that you should try to improve the air quality in your home even if symptoms are not noticeable.

Costanzo offered a practical note to the health issues. "If you smoke, your air system will need maintenance more frequently." And he added that, should you have toxic mold issues, you should have the mold abated by a licensed abatement contractor.

Better air
There are three basic strategies to improve indoor air quality, according to the EPA: source control, improved ventilation and air cleaners.
Source control: Usually the most effective way to improve indoor air quality is to eliminate individual sources of pollution or to reduce their emissions. Some sources, such as those that contain asbestos, can be sealed or enclosed; others, such as gas stoves, can be adjusted to decrease the amount of emissions. In many cases, source control is also a more cost-efficient approach to protecting indoor air quality than increasing ventilation because increasing ventilation can increase energy costs.

Ventilation improvements: Most home heating and cooling systems, including forced air heating systems, do not mechanically bring fresh air into the house, the EPA says. Opening windows and doors, operating window or attic fans, when the weather permits, or running a window air conditioner with the vent control open increases the outdoor ventilation rate. Local bathroom or kitchen fans that exhaust outdoors remove contaminants directly from the room where the fan is located and also increase the air exchange.

As you might expect, it is important to take as many of these steps as possible to increase ventilation while you are involved in activities that generate high levels of pollutants - such as painting, paint stripping, heating with kerosene heaters, cooking or engaging in maintenance and hobby activities such as soldering, or sanding. And both the EPA and common sense suggest you do as many of these activities as you can outdoors or at least in the garage.

Air cleaners: There are many types and sizes of air cleaners on the market, ranging from relatively inexpensive table-top models to sophisticated and expensive whole-house systems. The EPA indicates some air cleaners are highly effective at particle removal, while others, including most table-top models, are much less so. And air cleaners are generally not designed to remove gaseous pollutants.

The effectiveness of an air cleaner depends on how well it collects pollutants from indoor air (expressed as a percentage efficiency rate) and how much air it draws through the cleaning or filtering element (expressed in cubic feet per minute). As explanation the EPA notes that a very efficient collector with a low air-circulation rate will not be effective, nor will a cleaner with a high air-circulation rate but a less efficient collector.

Air filters
Your first defense against indoor air pollution (after reducing emissions at the source) is your Heating, Ventilating and air conditioning (HVAC) filter, your "furnace filter." The EPA indicates that, whether installed in the ducts of HVAC systems or used in portable air cleaners, most air filters have a good efficiency rating for removing larger particles when they remain airborne. These particles include dust, pollen, some molds, animal dander, and those that contain dust mite and cockroach body parts and droppings. (Ye-uuck!)

But because these particles settle rather rapidly from the air, air filters are somewhat ineffective in removing them from indoor areas, the EPA says. And although human activities such as walking and vacuuming, or the high-velocity air exiting supply vents, can re-suspend particles, most of the larger particles will resettle before they enter the HVAC system or portable air cleaner - so they won't be removed by a particle air filter.

The appropriate type of particle removal air filter can be chosen by looking at its Minimum Efficiency Reporting Values (MERV) rating in removing airborne particles from the airstream that passes through it, and the EPA notes that MERV ratings can also be used to compare air filters made by different manufacturers.

"What MERV you need will depend on your system," Costanzo said. "And we often use Honeywell high-efficiency filters." He suggested visiting www.honeywell.com for information.

Because of their compact design, particle air filters that use "impregnated media" are available for residential HVAC systems and portable air cleaners. They use sorbent particles of carbon, permanganate alumina, or zeolite incorporated into fibrous filter media, the EPA says.

Such filters provide a combination of particulate and gas-phase filtration with a minor increase in pressure drop across the filter. Their use in an existing HVAC system does not require extensive or expensive modifications to the system. However, the EPA cautions that their useful service life varies according to indoor pollution concentrations and exposure time.

But Costanzo said it's a good idea to "replace your filter every 30 days with a high-efficiency filter."

He added that this is especially important if you live near a freeway and after brush fires that put a lot of soot into the air. He also recommends regular visual inspections of ventilation ducts, evaporative coils and blowers. When dust builds up on these it reduces the efficiency of your HVAC system and also reintroduces these particles into the air inside your home.

Flat or panel air filters with a MERV of one to four have low efficiency on smaller airborne particles, but reasonable efficiency on large particles when they remain airborne, the EPA says. These filters have low airflow resistance and are relatively inexpensive. They are commonly used in residential furnaces and air-conditioning systems, and they are often used as pre-filters for higher efficiency filters.

"A MERV of one to five works well without getting clogged," Costanzo said.

Pleated or extended surface filters with a MERV of five to 13 have higher efficiency ratings than panel filters. These medium-efficiency filters are reasonably efficient at removing small-to-large airborne particles. The airflow resistance of these filters does not necessarily increase as the MERV increases. Costanzo explained that if your filter has too much resistance to airflow it will reduce the efficiency of your system in its heating and cooling. He added that most home systems are not designed for ultra-high efficiency filters because of this pressure loss.

"I'd recommend a MERV of one to five for most home use," he said. And he explained that the prices of these filters will vary according to their size.

So, with a little common sense, a little more ventilation and a good air filter, you just might win the battle against indoor air pollution. For more details, visit www.epa.gov/iaq/ or consult an indoor air professional.

Air Masters, Inc. is located at 28348 Constellation Road, #860, Valencia, CA 91355. The phone number is (661) 294-9022. E-mail airmastersinc@att.net.