3.16 Indoor Air Quality Standards in the United States 79
3.16 Indoor Air Quality Standards in the United States
In the previous section, we discussed outdoor air pollution and the related health effects. Indoor
air pollution can also create health risks. According to EPA studies of human exposure to air
pollutants, the indoor levels of pollutants may be two to five times higher than outdoor levels.
Indoor air quality is important in homes, schools, and workplaces. Because most of us spend
approximately 90% of our time indoors, the indoor air quality is very important to our short-
term and long-term health. Moreover, lack of good indoor air quality can reduce productivity
at the workplace or create an unfavorable learning environment at school, causing sickness or dis-
comfort to building occupants. Failure to monitor indoor air quality (IAQ) or failure to prevent
indoor air pollution can also have adverse effects on equipment and the physical appearance of
buildings. In recent years, liability issues related to people who suffer dizziness or headaches or
other illness related to “sick buildings” are becoming a concern for building managers. Accord-
ing to the EPA, some common health symptoms caused by poor indoor air quality are- headache, fatigue, and shortness of breath;
- sinus congestion, coughing, and sneezing;
- eye, nose, throat, and skin irritation; and
- dizziness and nausea.
As you know, some of these symptoms may also be caused by other factors and are not neces-
sarily caused by poor air quality. Stress at school, work, or at home could also create health
problems with symptoms similar to the ones mentioned. Moreover, individuals react differ-
ently to similar problems in their surroundings.
The factors that influence air quality can be classified into several categories: the heating,
ventilation, and air-conditioning (HVAC) system; sources of indoor air pollutants; and occu-
pants. In recent years, we have been exposed to more indoor air pollutants for the following rea-
sons. (1) In order to save energy we are building tight houses that have lower air infiltration or
exfiltration compared to older structures. In addition, the ventilation rates have also been
reduced to save additional energy. (2) We are using more synthetic building materials in newly
built homes that could give off harmful vapors. (3) We are using more chemical pollutants,
such as pesticides and household cleaners.
As shown in Table 3.9, indoor pollutants can be created by sources within the building or
they can be brought in from the outdoors. It is important to keep in mind that the level of
contaminants within a building can vary with time. For example, in order to protect floor sur-
faces from wear and tear, it is customary to wax them. During the period when waxing is tak-
ing place, it is possible, based on the type of chemical used, that anyone near the area to be
exposed to harmful vapors. Of course, one simple remedy to this indoor air problem is to wax
the floor late on Friday afternoons to avoid exposing too many occupants to harmful vapors.
Moreover, this approach will provide some time for the vapor to be exhausted out of the build-
ing by the ventilation system over the weekend when the building is not occupied.
The primary purpose of a well-designed heating, ventilation, and air-conditioning (HVAC)
system is to provide thermal comfort to its occupants. Based on the building’s heating or cooling load,
the air that is circulated through the building is conditioned by heating, cooling, humidifying, or
dehumidifying. The other important role of a well-designed HVAC system is to filter out the con-
taminants or to provide adequate ventilation to dilute air-contaminant levels.Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀