Theatre Design & Technology - Summer 2022 - 10

exhaust fan and an intake vent with a
MERV 13 air filter, which removes more
than 90 percent of particulate matter
PM2.5
or larger. The fan and filter were
able to create an environment inside the
chamber with significantly lower levels
of particulate matter than the outside air,
keeping the testing environment independent.
The PM levels were measured
every 80 seconds by PurpleAir PA-II-SD
sensors, one outside the chamber and
one inside, mounted one foot above the
material.
Before testing, 40 cubic inches of each
Materials were dried and tested for particulates 2.5 microns or smaller (PM2.5) in a testing chamber with
MERV 13 filtration. Each material was agitated as the surrounding air was tested for one hour. | Images
courtesy of Brad Steinmetz.
then taken of each piece of fabric and
the digital images were compared before
and after laundering to determine
the overall reduction in lightness of the
fabric. (Digital image analysis involved
identifying the average color of the darkest
one-third-inch square before and after
laundering. Three individual lightness
values of the color were averaged to create
a total percent reduction in lightness.)
As logic would suggest, dyed mulches
stain fabric more significantly and more
permanently than most. Staining from
Topsoil 1 washes out very well as does
that of Peat Moss 2, which happens to
have a lower moisture content out of
the bag than Peat Moss 1, which did not
fare as well. (Peat is a type of soil created
when plant materials submerged
in bogs break down over thousands of
years. The most common type of peat is
from the sphagnum moss plant, which is
the source for Peat Moss 2. By contrast,
Peat Moss 1 is composed of darker sedge
peat. These differences may have also affected
the results.) There is a moderate
correlation between staining and moisture
content where wetter materials tend
to stain somewhat more. Contrary to expectations,
neither the synthetic nor the
natural fabrics consistently stained more
significantly than the other type.
With respect to air quality, it would
be impossible to produce side-by-side
comparisons for all 15 materials in full
production situations. Instead, this study
compares the amount of airborne particulate
matter for each material in a unique,
controlled environment. A 100-cubic-foot
test chamber was built that included an
10 | THEATRE DESIGN & TECHNOLOGY | SUMMER 2022
material was baked at 200 degrees for
six hours in an effort to bring each to a
similarly low moisture level. Each material
was placed in a tray, along with
three billiard balls to help agitate, and
then secured to the platform of an orbital
lab shaker located inside the test chamber.
During each test, the chamber was
closed, and the filtration system ran by
itself for 15 minutes to clear the air, after
which the lab shaker was turned on and
ran one hour. PM2.5
levels were tracked
throughout the process and graphed over
time.
Although Topsoil 1 produces the
least airborne particulate matter, the
other two topsoils produce the most,
the highest being Topsoil 3 with an average
level of 28.09 µg/m3
. This may be
the result of the differences between
bags of nursery topsoil, normally a
custom mixture of materials like peat,
sand, and soil amendments, and bulk
topsoil, which is generally harvested
from a greenfield site, sifted in various
ways and sold by the truckload.
Unfortunately, the specific origins and

Theatre Design & Technology - Summer 2022

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