Hatchfield, 2014: MINIMIZING DAMAGE IN STORAGE AND DISPLAY
critical to understand the chemical nature of
Table 2: Indoor sources of pol ution
Nitrogen
Fuel combustion; cellulose
materials found in the collection, in addition to
oxides
nitrate degradation
understanding housing materials and the museum
Acidic materials from
environment.
Furthermore,
many
gases
Sulfur oxides
manufacturing processes
considered stable under normal circumstances
Hydrogen
Construction materials, wood,
react readily in the presence of certain chemical
sulfide
rubber, paints
species such as free radicals that may be created
Carbonyl
None
in photochemical reactions. Light will enhance
sulfide
degradation processes for many materials. For
Construction materials,
example, the degradation of leather in the
Acetic acid
especially wood products,
presence of sulfur dioxide can produce the
adhesives, sealants
phenomenon of red rot (see also Rae, this
Construction materials, surface
Formaldehyde
volume).
finishes, paints, adhesives,
coatings
It is also important to consider the potential for
Oxidation of formaldehyde,
damage
by
particulates,
or
dust.
Typically
Formic acid
paints coatings
hygroscopic and usually abrasive, they act as
Photocopiers, printers,
nucleation sites for corrosion on metals, or
Ozone
particle filters
chemical interactions on other materials. They are
Hydrogen
Alkyd paints
generated
in
the
exterior
environment
by
peroxide
biological
processes
such
as
combustion,
Combustion, heating,
microorganisms and decay, and non-biological
Particulates
carpeting, HVAC, copiers,
elements
like
salts,
vehicular
traffic
and
concrete, plaster
construction
(Table
1).
Indoors,
they
are
Ammonia,
alkaline
produced by combustion processes such as
Cleaning agents, paints
aerosols
cooking or heating, construction processes, soiling
and textiles (Table 2). New materials brought into
More than 900 VOCs have been identified in
collection environments, either for construction or
indoor environments, 250 of them at greater
storage housings contribute significantly to the
than 1 parts per billion (ppb). As an example,
overall quality of air in the building. Building
consider that silver tarnishes at 0.2 ppb
materials like wood products, insulation, wall
hydrogen sulfide. In a typical museum
coverings, paints, floor finishes or ceiling tiles can
environment, hydrogen sulfide is typically
be significant sources of pollutants, especially
found at higher levels than this, and in some
when large surface áreas are involved. The
exhibition cases has been measured at as high
volatile
organic
contente
(VOC)
of
many
as 50 ppb. Many other examples of alteration
construction materials may be extremely high.
of collection specimens like limestone, metals,
VOCs in construction materials have high vapor
organics and synthetic materials have been
pressures and will continue releasing chemicals,
documented (Hatchfield, 2002: 32-42).
attempting to come into equilibrium with their
In
addition
to
the
collection
objects,
concentration in the surrounding air.
construction and preparation materials brought
in to house objects must be carefully
considered. Particularly with old display or
Table 1: Outdoor sources of pol ution
storage cases and historic exhibits such as
Combustion (diesel, coal) and
dioramas, construction materials are likely to
industrial production; agricultural
be a source of pollutants. These may include
Nitrogen
fertilizers; lightning; smog
wood products, oil paints, plant fibers, plastics,
oxides
increased 17% since the U.S.
oil-based clays, waxes, and many materials
Clean Air Act of 1970
used in taxidermy.
Combustion, energy and
Sulfur oxides
industrial production; paper
plants; refineries
Testing for pollutants
Hydrogen
Bioeffluents, combustion
Testing for pollutants is often done at the
sulfide
Carbonyl
Biochemical sources,
building
level.
Information
about
the
sulfide
geochemical processes
environment within the building is particularly
Ozone
Light, high temperatures
valuable to compare to the exterior, and also to
Combustion, road salt, organic
the pollutant levels within display cases. These
Particulates
matter
comparisons can help identify the locations, if
Ammonia/
not the sources of problematic pollutant species
alkaline
Microbial activity, fertilizers
(Grzywacz, 2006). Rather than requiring
aerosol
sophisticated equipment, some companies offer
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Journal of Paleontological Techniques