Page 301 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

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Since the VOCs contain a range of many compounds of various molecular weights, the
limits given are in the units of mass per volume instead of air molar or volumetric based
ppm or ppb (parts per million or billion).
PM10 has been described in detail earlier in IEQc3.1. Particulate matter contains a
range of many compounds, and these are in either solid or liquid form. Since particulate
matter is not separate gaseous compounds, the limits given are in the units of mass per
volume of air instead of ppm. Unacceptable levels of PM10 may mean that there are still
many leftover sources from the construction phase in the building or HVAC system
and/or that there are pathways from other sources into the occupied areas.
4-Phenylcyclohexene (4-PCH) is applicable only if certain carpet and fabric backing
binders are used. Its odor is commonly referred to as “new carpet smell.” Each molecule
of 4-PCH is made up of 12 carbon atoms and 14 hydrogen atoms.
Carbon monoxide is a commonly known air pollutant that, in high enough quantities,
can cause death from asphyxiation. It is a product of incomplete combustion from any
carbonaceous fuel source. There are two indoor limits given. The first is a maximum in
any case, and the second is a limit for the value above the outdoor levels. Many buildings
are located in urban areas where motor vehicle emissions and other emissions from
combustion can give an elevated outdoor CO level. In all cases, the maximum value
inside should not be more than 2 ppm above the outside. As per the EPA, the national
ambient air quality standard (NAAQS) for CO is 9 ppm 8-h nonoverlapping average not
to be exceeded more than once per year. (There are some areas in California, Montana,
Nevada, Oregon, and Texas which are currently in nonattainment of the standard.)
As outlined in the LEED-NC 2.2 and 2009 Reference Guides, the air quality testing
should be performed in the breathing zone (see Fig. 6.0.1) during typical occupancy
hours and with the minimum air rates that will occur during occupancy, in addition to
several other detailed prescriptive requirements. In this way, the tests will measure
what is expected to be the worst background conditions related to the facility but not
directly related to human activity in the building. If tests fail, then after corrective action,
new tests need to be performed in the same locations.

Special Circumstances and Exemplary Performance
It may be difficult to fully understand the varied units and multiple requirements in
this credit, and for other indoor air quality requirements for green facilities. Therefore,
some additional information about air pollution calculations and conversions is given
at the end of this chapter, and a listing of the units used can be found in App. C.
Several criteria should be considered in the design and construction phase if this
credit is sought:

• The flush-out flow rates should be considered, and if the permanent HVAC
equipment is not expected to accommodate these flush-out rates in a timely
fashion, then some additional temporary units may be needed and/or openings,
such as windows, positioned to facilitate the desired level of air exchange.
• If a project is done in phases, then the flush-outs may be phased, but all the
SNACNA principles must be adhered to between each phase.
• As mentioned previously, this credit is not directly applicable to core and shell
projects until the interiors are complete.
• Chemicals are often used prior to occupancy to prepare and “clean” a facility. If
high-VOC chemicals are used, then these may alter the results. They should be
avoided.