VOC Emissions from Standard and Alternative Materials Used in New Relocatable Classrooms
Investigation of VOC emissions from materials used to finish the interiors
of new relocatable classrooms
Relocatable classrooms (RCs, also know as portable or modular classrooms)
are widely used in California to help satisfy school districts' expanding
space requirements due to population growth and class size reduction
policies. There has been concern regarding indoor environmental quality
in these schools, but very little data to support or dispel the concerns.
In 2001, the IED conducted a laboratory investigation to evaluate the
release to air of toxic and/or odorous VOCs, including formaldehyde,
from standard and alternate materials used to finish the interiors of
new RCs (Hodgson et al., 2001). These materials were
to be used to finish the interiors of four new RCs that were constructed
and studied in the second phase of the investigation.
Procedures for Measuring VOC Emissions from Classroom Materials
Seventeen recently manufactured specimens of standard and alternate
materials within the categories of carpet, resilient flooring, tackable
wall panels and acoustical ceiling panels were obtained from the RC
production facility and from the material manufacturers. These materials
are listed in Table 18.
Test specimens, typically with exposed surface areas of 0.02
m2, were cut from the larger pieces. The test specimens were
preconditioned for ten days in small chambers immediately prior to a
96-hour VOC emission test. The parameters used for conditioning and
testing of the specimens are shown in Table 19.
VOC emission rates (mass per time) and emission factors (mass
per area-time) were calculated for the chamber tests using the steady-state
form of the mass-balance model for well-mixed chambers (ASTM
Standard Guide D5116-97). The VOC emission factors for each material
were multiplied by the projected surface area of the material exposed
in a RC to produce estimates of classroom emission rates. Then for each
compound, the emission rates were summed across all materials in a standard
or source modified classroom. Predicted indoor VOC concentrations were
estimated by dividing the summed emission rates by flow rates of outside
air for different ventilation rate scenarios.