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Sat 20 Dec 2008 04:00 AM

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How good is the air you breathe indoors?

John Vasselli, chief of technology for indoor air quality at the Carrier Corporation tells us how the air we breathe indoors can affect our health and productivity.

John Vasselli, chief of technology for indoor air quality at the Carrier Corporation tells us how the air we breathe indoors can affect our health and productivity.

People spend about 90% of their time indoors - even in milder climates. The quality of our indoor environments can thus significantly impact, not just our comfort, but health and productivity as well - at home, work or school.

The rapidly growing demand for "green" buildings, emphasises energy efficiency as well as the importance of indoor air quality (IAQ). Real estate markets around the world are realising that buildings constructed with emphasis upon good environmental quality sell or rent more rapidly, at higher prices, and with fewer turnovers. This is because a large number of credible studies show that the occupants of such buildings are healthier and happier.

IAQ makes all the difference

Some facts derived from studies around the world have shown that IAQ improvements result in a reduction of short-term and chronic respiratory illness in the office workplace environment by 9% to 20%. They also achieve higher levels of work related productivity, ranging from a 1% to 4% improvement as measured by speed, accuracy and other subtle aspects of decision making.

Trends in IAQ

The increase in illnesses due to indoor air quality is the result of several factors. The first is that increasing emphasis upon energy efficiency in buildings has resulted in building envelopes being built much tighter, thus allowing far less air to leak in and out.

Increasingly we are living and working in environments that are designed to keep us isolated from outdoor climate conditions. Those "tighter" environments are causing increased accumulation of indoor contaminants that are at the source of IAQ concerns.

Compounding this trend is the outside air that's getting worse due to the increased burning of fossil fuels and global warming and associated climate change. This is especially true in large urban environments, where high concentrations of small particles, gases generated by vehicles, power plants, industrial sources or ozone in the atmosphere contribute to increased death rates.

Increasingly, people will seek shelter indoors from poor outdoor air quality. Unfortunately, in many buildings, the indoor air quality is much worse (five times worse in the US) than the outdoor air quality.

This is because indoor sources of airborne contaminants release harmful chemicals present in building materials, clothing, furnishings, carpeting, paints, fire retardants, cleaning materials, and equipment such as copiers. As we tighten our building envelopes to save energy and reduce outdoor air from infiltrating indoors, we create indoor environments where contaminants build-up in concentration.

Factors impacting IAQ

Three specific airborne contaminants most commonly found indoors are worth noting. Studies of indoor environments indicate that the most commonly found gas, formaldehyde, is also the most harmful to humans. It is a carcinogen, and is found at average concentrations that are more than 20 times higher then safe levels recommended by the medical community.

The second contaminant is ozone, a highly reactive gas generated both by indoor sources and outdoor sources. The third contaminant type is airborne particles, especially particles that are smaller than 2.5mm in diameter.

That's about 20 times smaller than the diameter of a human hair - therefore not visible to the human eye. Both ozone and fine particles when breathed into the lungs cause proven increases in illness and death. The presence of all three of these contaminants is increasing around the world.

A breath of fresh air

So what is the solution to improving IAQ? In climates where occupants can "open the windows" to get "fresh air," the accumulation of indoor airborne contaminants is significantly reduced.

However, in many climates outdoor temperatures and/or humidity levels make "opening the windows" an unattractive option for reducing indoor pollutants via dilution using outdoor air.

Also, as we have just discussed, in many locations, outdoor air quality is poor because of high levels of dust, vehicle exhaust, or industrial process gases that result in the generation of fine particles, ozone, and hundreds of hazardous airborne pollutant gases, many of which are carcinogenic.

To a building, the heating, ventilation and air conditioning (HVAC) system acts as the "lungs" of that structure. When designed and operated properly, the system knows when to breathe in and out, bringing in fresh air, conditioning it to adjust for temperature, humidity and to remove contaminants from coming indoors.

However, the cost (in energy) to condition outside air can be significant if outside temperatures and humidity levels must be significantly altered to match indoor conditions. Therefore, HVAC systems also re-circulate air, passing it through filters that remove particles, gases and even kill airborne molds, bacteria and viruses.

Healthy environs

To accomplish this higher level of IAQ performance, HVAC systems offer a range of higher efficiency filters. For particle removal, such filters are rated using an "F" scale, where the higher the "F" number, the better the filter is at removing particles. Most green building organisations recommend particle filters that achieve F7 performance. Such filters remove approximately 85% of particles in the air in a single "pass" through the HVAC filter.

Taken in combination, today's HVAC technology can create an indoor air quality "oasis," where not only comfort, but a healthier and more productive environment can be created indoors. Breathe well!

If you would like to write for Construction Week in this column, please email rob.wagner@itp.com.

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