Indoor Air Quality

5/2/2011

During the late 1970’s, when America experienced its first major energy crisis, and we saw lines of cars wrapped around city blocks waiting over an hour to fill up their cars with precious gasoline (they had leaded in those days!), a number of initiatives (I am hesitant to use the word “solutions”) were instituted. For reducing the long lines at the gas pumps, alternating days were assigned as either odd or even, so that, depending on the number of your license plate, determined what days you were permitted to fill up (there were no personalized licenses back then either, so today’s plates having a message would be SOL).  

Another practice to reduce energy usage was to recycle air in building ventilation systems.  So when heating, ventilation and air conditioning (HVAC) units actually brought 100% fresh air from outside the building and then heated/cooled it and distributed it throughout the office environment, now recycled a significant portion of its air and made up the difference with anywhere from 20-50% of fresh air.  As a result, HVAC systems were/are often categorized based on is recycled/fresh air ratio. For instance, an 80/20 system, indicates that 80% of the air is recycled and 20% is actual fresh air.  Today, many systems can vary the recycled/fresh air ratios based on outside temperatures. If it’s extremely cold and hot outside, less fresh air enters the building than when we are having beautiful spring or fall weather.  The idea is to reduce heating/cooling costs.

This practice of recycling indoor air resulted in an unforeseen event: Indoor Air Quality (IAQ) or sometimes called “Sick Building Syndrome.”   That is, because air was being recycled, gases like carbon dioxide (CO₂), created due to human exhalation, were being accumulated in the office environment.  This caused many workers to experience drowsiness and lethargy; and while CO₂ is considered a simple asphyxiant (displacing oxygen), such a concentration within a building is not feasible (however, in smaller quarters such as the Apollo 13 Space Module this was a real concern), CO₂ can reach levels of 1000 parts per million (ppm): typical outside air concentrations are 300 ppm.   

While recycled air is considered an accepted practice, organizations such as the National Institute for Occupational Safety and Health (NIOSH) and the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) have established health guidelines for office environments. This includes no more than 800 ppm of CO₂ and at least 20 cubic feet per minute per person of fresh air.  When these levels are not met, building maintenance needs to readjust or balance the HVAC system. 

In addition to CO₂, odors from perfumes and colognes may also accumulate and trigger or exacerbate the allergies or sensitivities of fellow-employees.  By the 1980’s IAQ became a major issue that resulted in employee complaints, absentee, as well as law-suites. As a result, today there are many office environments that have established “fragrant-free environment” policies.   Many times, industrial hygienists were brought in to perform formal investigations so that the source of an employee concern could be properly addressed.  In many cases, the solution involved increased air flow as well as ensuring the office temperatures were within employee comfort levels. Obviously comfort is a very subjective matter, whereby what one employee may consider acceptable, another may not.

Another concern can be odors from furniture and carpets.  For furniture, specifically wood (including particle board or press board), formaldehyde is an issue.  In such cases, formaldehyde is used in the fabrication process as an adhesive and would result in “off-gassing” over a period of time.  Naturally, due to the newly established energy-saving recycled process, accumulation of formaldehyde became a potential concern.  Once again, by applying proper ventilation, formaldehyde off-gassing can be controlled.

Carpet is one type of floor covering that is commonly used in homes, commercial buildings, schools, cars, and public facilities. IAQ issues often associated with carpet range from odor and off-gassing of organic vapors from the carpet backing or adhesive, to retention of allergens from dust mites and pet dander. A carpet that is poorly maintained or water damaged may result in fungal contamination.

Like many other household products and furnishings, new carpet can be a source of chemical emissions. Most carpet used in residential, public, and commercial settings consists of synthetic pile, usually nylon or olefin, cut pile or nylon tufted through a primary backing with a back coating of solvent-based adhesive. The loop of the tufted pile is set into a styrene-butadiene rubber (SBR) latex base, which is sandwiched between backings made of woven polypropylene or jute. Other common carpet types in schools and office buildings include carpet tiles usually made with a hard backing of polyvinyl chloride (PVC) or hydrocarbon resin. The new carpet odor that people may smell after carpet is installed is usually 4-phenylcyclohexene (4-PCH), which is a by-product of the styrene butadiene latex binder, used to hold the fibers to the backing. This chemical has a very low odor threshold, which means it can be in the air at very trace levels and still be detected by the human nose. Toxicology studies have shown that 4-PC is not a health hazard at the levels experienced from carpet, but that it does contribute an odor. Generally, the emissions from new carpet are at very low levels one week after installation and odors should go away within a short time.  Through vacuuming and ventilation, employee concerns due to VOC off-gassing from carpets can be mitigated.

4-phenylcyclohexene

Obstacles are those frightful things you see when you take your eyes off your goal. 

Henry Ford