Home Air Quality

People spend at least half of their lives inside their homes. Most people think of the home as a safe sanctuary but the air inside can be more harmful to your family’s health than the air outdoors. It is not always easy to tell if your home has poor air quality. You may notice bad smells, dust or see smoke, but you cannot see or smell other dangers, like carbon monoxide, volatile organic compounds (VOC), allergens like pollen or dust or radon.

Here are four quick and easy ways to improve the air quality:

1. Change your furnace filter regularly and consider upgrading to a hypoallergenic filter. A hypoallergenic filter will improve your indoor air quality by capturing allergy-aggravating particles such as dust, mold spores, pet dander and pollen.  However because these filters are denser they will need to be changed more often. 3M makes a line of hypoallergenic filters that  are rated very well. 3M publishes replacement guidelines and if they are not followed it will shorten the life of your furnace.

2. Add an externally venting hood to your kitchen. Most builders do not vent the range hood to the outside. Many homeowners discover this the first time they burn something on the stove and find out the hood fan doesn’t remove  the smoke. Cooking releases moisture, oils, smoke andcombustion by-products. Although many of these smells are pleasant many of the by-products are not healthy for you. An externally vented range hood will remove many of these odors and ultimately make your house smell better.

3. Add a filter system to remove dust and organic allergens. These are a step above replacing your furnace filter and remove finer particulars. Whole house electronic filters from Aprilaire, Honeywell or Trane filter systems are readily available for approximately $500-$600and can easily be installed by a qualified heating and air conditioning technician. Room size air purifiers are also available but before you run out and buy one such as Sharper Image’s Ionic breeze, I suggest you read what Consumer’s Report has to say about it. They have released a new report in the May 2005 issue. In the past they have recommended the Honeywell’s Enviracare orFriedrich’s C-90A room filters.

4. Use a vacuum with a HEPA filters. Almost all dust originates outdoors and is brought inside where it ends up on the floor or is trapped in the carpeting. Cleaning your floors with a common vacuum cleaner will only make the dust problem worse as the vacuum bag only traps the larger particles and sends the smaller particles swirling back into the home. A vacuum with a HEPA filter will reduces this problem dramatically. An even better solution is a whole house vacuum with an outdoor exhaust.

For most home owners the sure path to energy efficiency in houses is eliminating air leaks. If you cut down the amount of air that has to be heated and cooled, you cut your utility bill substantially. But plugging up all those air leaks means less fresh air inside and this has brought on other problems.

Volatile organic compounds were one of the first indoor pollutants to be identified as having elevated concentrations in the air. Commonly called VOC’s, these compounds are used in the manufacture of the many synthetic building products used in most new houses today, including carpeting, flooring, paint, cabinetry, countertops, and the structural framework itself. Hundreds of off-gassing VOC’s have been identified, but the one that has captured the most attention is formaldehyde. It is a potent eye and nose irritant and causes respiratory effects. It is also classified by the US Government Environmental Protection Agency as a probable human carcinogen.

In response to the concerns raised by health officials and the public over the last fifteen years, manufacturers of some building materials and furnishings have altered their chemical formulations, significantly reducing the amount of VOC’s off gassing from their products.

A brand new house will still have a significant amount of VOC’s in the air because the rate at which the VOC’s off-gas is highest initially. This phenomenon accounts for the “new house smell” that most new house buyers experience. Delaying a move-in and airing out a house by opening all the windows and running all the exhaust fans will benefit the occupants, even if this is done for only two days, advised John Girman, Director of the Center for Analysis and Studies for the Indoor Environmental Division of the US Government Environmental Protection Agency.

Continuing to keep the windows open and ventilating the house for several day to several weeks, if weather permits, can also be beneficial, added Al Hodgson of Lawrence Berkeley National Laboratory in Berkeley, California, who has been studying indoor air quality for the last 18 years.

After the first month or so, the rate at which the VOC’s off gas from building materials may fall off, but Hodgson’s research indicates that the off-gassing phenomenon will continue at a slow and steady pace for months or even years. Hodgson measured the indoor air quality in eleven new, but unoccupied houses one to two months after their completion. Some were monitored over a period of about nine months. Overall he found that the concentrations of VOC’s in the houses were not “alarming,” although the concentrations of some compounds were high enough to produce an odor. The levels of formaldehyde were too low to have a smell, but high enough to cause discomfort in some individuals.

Although the level of VOC’s in new houses does fall off over time, buyers can reduce it at the outset by their selection of finishes. Hodgson’s research has shown while carpets are generally low emitters of VOC’s, a reasonable quality, medium-grade, nylon, certified green label carpet may emit less than the basic grade carpet that most builders offer as standard. Installing the carpet with tack strips instead of an adhesive eliminates a potential VOC source altogether. Synthetic fiber carpet padding emits less than the rebonded padding that most production builders provide.

Hodgson’s “certified green label carpet” refers to the green and white Carpet and Rug Institute emission test sticker found on carpeting that meets their emission standard. Their testing program was established after sensational stories about “killer carpets” appeared in newspapers and TV news programs in the early nineties. In a New England lab, mice were exposed to carpet samples and subsequently died. Scientists in other labs including the EPA were never able to replicate these results and the reason for the mice’s demise remains unclear.

After the Carpet and Rug Institute started its carpet-testing program, it raised the emission standards, which has further reduced carpet emissions. Even so, carpeting can still have an odor that makes people think that they are being exposed to something awful, Hodgson observed. Vinyl flooring is a stronger emitter than carpet, but it too should not be a cause for concern, Hodgson said.

The oil-based alkyd and water-based latex paints used in most houses are another source of VOC’s. The alkyds, which create a harder, more washable surface, are usually used for bathrooms, kitchens, and the trim around doors, windows and baseboards. They produce a terrible smell and emit hundreds of VOC compounds, but these are almost entirely dissipated after about 48 hours, said John Chang, of the EPA labs in Triangle Park, North Carolina. The latex paints have a different smell and emit only four or five VOC compounds, but these continue to off gas for days and weeks after the paint is dry. “Low VOC” latex paints are now available, but some of these emit formaldehyde and buyers should check the paint emission data, he advised.

Hodgson is currently studying the man-made wood products used in residential construction because most of them contain formaldehyde, and formaldehyde concentrations in the indoor air of new houses have been found to be higher than in other building types. Large quantities of these wood products including cabinet materials, doors, door and window trim and baseboards are found in the finished space of new houses. Man-made wood products are also used extensively in their structural framework. Hodgson is looking at the emissions of formaldehyde and VOC’s from each product as well as the amount of exposed surface of each product. He is finding that bare surfaces of wood products can have relatively high emissions, but that surfaces with laminate and vinyl finishes generally have low emissions.

In some cases, products that are considered to be low emitters are turning out to be a significant source of VOC’s when viewed in the context of the whole house, Hodgson said. For example, formaldehyde and other VOC’s given off by the oriented strand board or plywood used for the subfloor in most new houses today are low when calculated on a square foot or a per piece basis. But Hodgson’s research is showing that when the total area of the subflooring in a typical house is taken into account, it can be a significant VOC source and that the overlying carpet and carpet padding are not effective barriers.

Other research in indoor air quality in new houses has focused on the problem of underventilation. Until the last 20 years or so, mechanical engineers could reasonably assume that between air leaks and occupants opening the windows, everyone was getting plenty of fresh air. But as houses have become tighter, less outside air is penetrating through air leaks and with air conditioning; no one opens the windows in the summer anymore.

To rectify this situation, the American Society for Heating, Refrigeration, and Air Conditioning Engineers, commonly known as ASHRAE, proposes that mechanical ventilation be required in all new houses, as it is in most commercial and office buildings. The engineers have not dictated how this should be accomplished, and the desired ventilation rate varies with the size of the house and the number of bedrooms. For a 2,400 square-foot house with four bedrooms, for example, the proposed rate would be .35 changes per hour. At this rate, all the air in the house would be replenished every threehours.

Some homebuilders have suggested that ASHRAE’s ventilation proposal could add $1,500 to $6,000 to the cost of a new house, but ASHRAE’s proposal could be easily and inexpensively done. One continuously running 100 cfm bathroom exhaust fan that is exhausted to the outside would do the job for a 2,400 square foot house and this modification would cost only $75 to $100 more than the exhaust fan and venting that the builder would already be installing in the bathroom, said Max Sherman, also of the Lawrence Berkeley National Laboratory, who has studied indoor air for 20 years. Putting a smaller continuously running fan in each bathroom is a more expensive solution, but it would distribute the fresh air more evenly.

The ASHRAE proposal includes a sound recommendation for the continuously running fan because occupants turn fans off when they’re too noisy. The dedicated exhaust fan should have a sound level of one sone or less so that it won’t disturb a household at night when the ambient noise level is low.

Relocating the air-handling unit from the garage to some other place in the house would also improve indoor air quality, Sherman said. In some parts of the country such as Florida and California, houses do not have basements and the air handling equipment is often put in the garage. Unfortunately the ducts for the system often leak so that if a car engine is left running for any length of time, homeowners can unwittingly introduce carbon monoxide into their living areas.

Helpful links to more air quality source

Consumer Report Reprint -some air purifiers do little cleaning
California Air Resource Board Test Report on Air Purifiers that use Ozone
Care for your aire –  Guide to Major Indoor Air Pollutants in the Home
Residential Air-Cleaning Devices
Should You Have the Air Ducts in Your Home Cleaned?

Auto exhaust is thought to be the number # 1 cause of accidental CO poisoning in North America and has been reported to be the cause of around 60% of carbon monoxide alarm responses. Just notice how many people let their automobiles warm up inside garages with the door open and for how long before they back out and close the door with their automatic door control. Typically, any gasoline engine produces the highest CO levels during a cold start. CO gets trapped inside the garage and can easily disperse into the rest of the building through unseen but loose fitting construction connections (like wiring penetrations, framing joints, ductwork seams, door jambs and other areas). Building pressure and temperature variations work as siphon points and air exchange locations.

Every home should have a CO alarm. There are inexpensive and available at most home improvement stores. CO alarms come in many styles and range in price from under $20 to over $75. Generally the cheaper models only sound the alarm while the more expensive models will sound an alarm and display the CO level. Consumer Report’s tested CO alarms in October, 2001 and recommended models from Kidde and Senco as having superior performance.

Proper placement of a carbon monoxide alarm is important. If only installing one carbon monoxide alarm, the Consumer Product Safety Commission (CPSC) recommends it be located near the sleeping area, where it can wake you if you are asleep. Additional alarms on every level of a home will provide extra protection.

Carbon monoxide in homes does not always come from traditional sources. The service and HVAC industry has been targeting cracked heat exchangers as the leading source of CO poisoning (almost exclusively without test instrument verification until about 1985). Recent, more thorough testing for CO suggests that unvented, poorly installed, unmaintained and misused gas and oil appliances are the 2nd leading cause of CO alarm response, and may constitute as much as 20% of CO alarm call sources.

The 3rd leading cause of CO exposure appears to be due to vented atmospheric, natural drafting appliances which backdraft into the structure and may account for 19% of the CO alarms going off. Intermittent backdrafting of CO laden flue gases complicates source investigations. Improperly sized and installed vent systems, old vents in need of repair, and competing building pressures contribute to this affect. Even if no significant levels of CO are measured in the flue gases, keep your eyes open to indications that spillage is occurring during other periods of time. Soot or rust on draft hood surfaces or above the burner areas are common examples.

It should be noted that cracked heat exchangers make up one of the smallest percentages of CO alarm response causes (less than 1%). Unfortunately as furnace get older and receive little maintenance the opportunity for a crack grows larger. In many cases the HVAC technician only does a visual inspection of the furnace heat exchanger not knowing that the crack most often happen on the backside of the exchanger. The only certain way to check the heat exchanger is to have it leak tested.  In some cases a furnace with a cracked heat exchanger is condemned by a technician or utility personnel, red tagged and shut off only to be returned to operation by a homeowner. A furnace left in operation while a known crack exists represents a tremendous health, safety and liability concern and should be thoroughly tested for CO production. Test results can then be presented to the homeowner emphasizing a very real and present danger.