Page 300 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

LEED Indoor Envir onmental Quality 263

Air Quality Option The air quality option allows for occupancy as soon as it can be proved
that the air quality adheres to a minimum standard. Usually improved air quality is
attained by flushing out the spaces. Attaining these minimum standards may require
several more days of flush-out if areas are found not in compliance. There are five
groups of compounds for this air quality option: formaldehyde, particulate matter of
10-μm diameter or less (PM10), total volatile organic compounds (TVOC), carbon
monoxide (CO), and 4-phenylcyclohexene (4-PCH). (The 4-PCH needs only be measured
if there are carpets or fabrics installed as part of the base building with styrene butadiene
rubber latex backing material.) The maximum allowed concentrations as measured per
the prescribed methods are listed in the Requirements section.
Formaldehyde has the chemical formula H CO and goes by many other common
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names, such as methyl aldehyde. It is one of the most commonly used chemicals for
manufacturing and is commonly used as a preservative for many everyday goods. In
buildings, it is emitted from many pressed wood building materials, such as particleboard,
as an off-gas from the resins used. Formaldehyde is also one of the simplest organic
compounds and is a by-product of many chemical reactions including combustion, such
as in cigarette smoking or fuel burning or even from reactions within our own bodies.
Therefore, it is found throughout the spaces we occupy at low levels. Formaldehyde is a
good compound to test, because its presence at higher levels may mean that either there
is still substantial off-gassing of many construction materials and/or there are unacceptable
levels of combustion emissions entering the facility. A level of 0.1 ppm is considered to be
the level above which there may be eye, throat, or lung irritation. Common levels in
homes are usually well below this threshold for human irritation. However, homes with
certain insulations or a lot of pressed wood products, and poor ventilation, may reach
levels of up to 0.3 ppm. The U.S. Department of Labor Occupational Safety and Health
Administration (OSHA) has set a permissible exposure limit (PEL) for formaldehyde of
0.75 ppm [time-weighted average (TWA) in an 8-h workday] and a short-term exposure
limit (STEL) of 2 ppm for 15 min as per 29 CFR 1910.1048. The U.S. Department of Housing
and Urban Development (HUD) has established a maximum level of 0.4 ppm for mobile
homes. The standard in this credit is for formaldehyde to be less than 27 parts per billion
(ppb) or, equivalently, 0.027 ppm (it was 50 ppb in LEED 2.2).
TVOC is also commonly referred to as VOC and stands for total volatile organic
compounds (or carbons). It consists of many hundreds of organic compounds that are
volatilized. Organic compounds are defined as compounds which contain carbon
excluding the inorganic carbon compounds such as carbon monoxide, carbon dioxide,
carbonic acid, metallic carbides, and carbonates. The term VOCs usually includes all the
volatilized organic compounds except for a few exclusions due to low reactivity of these
specific chemicals. Emissions are regulated for VOCs by the USEPA because many
VOCs participate in atmospheric photochemical reactions, such as the smog reaction
which causes ozone to develop in the troposphere during the day. However, there are
no ambient air quality standards for VOCs as a total group. Some of the VOCs are
considered to be carcinogenic and may have individual concentrations set, such as
formaldehyde and benzene. Many VOCs are natural, such as limonene emitted by
citrus fruits and many emitted by pine trees or cut grass, which give those distinctive
smells to the air. VOCs can be by-products of combustion and represent much of the
evaporative portion of paints, glues, and other surface-applied products. Since it is not
reasonable to evaluate each and every VOC, they are regulated as a group. In addition,
their additive impact may be greater than the individual compound concentrations, so
minimizing the concentration of VOCs as a group is also helpful to health and property.