Series editors' preface - Wood Tools

266 Conservation of Furniture
though this is not brought about by adsorption
but by destruction of the ozone through
reaction with traces of organic matter on the
filter material. Charcoal filters are also capable
of removing organic free radicals such as
peroxy acyl nitrate. As with particulate
removal, this type of filter improves in
efficiency with recirculation of the air and
there should be no difficulty in reducing SO 2
and NO 2 levels to below 10 μg/m 3 and ozone
to trace levels (below 2 μg/m 3 ). Activated
carbon filters need to be changed when their
ability to absorb gases becomes diminished.
This has to be determined by experiment in
the first instance and a routine must then be
established for their renewal. Where air conditioning
is not available, the problem of air
treatment becomes rather difficult as show
cases have to be treated individually. Possibly
a carefully chosen alkaline reagent might be
useful in this respect. Although activated
carbon filters may lose much of their efficacy
unless air can be circulated through them,
experience has shown that charcoal cloth can
be effective in removing low levels of volatile
organic substances produced inside show
cases by the materials used in the construction
of the case. For more detailed discussion of
the causes, effects and control of air pollution
see Calabrese and Kenyon (1990), Goodish
(1990), Harrison (1992a, 1992b), Strauss and
Mainwaring (1984) and Thomson (1986).
6.2.6 Biological agents
Many biological hazards, ranging from very
small micro-biological agents such as bacteria,
through mildew, moulds, fungi and insects to
birds, rodents and other small mammals, have
the potential to affect furniture collections.
Damage between them may be interrelated.
Surface dirt may allow creation of locally high
RH that encourages mould growth which in
turn may promote insect attack. The detritus
that accumulates around pigeon nests on the
outside of a building may encourage the
growth and multiplication of insect pests such
as carpet beetle which then find their way
inside. Similarly, birds and small mammals
may die in chimneys or roof spaces forming
a source for insect infestation. Although it is
not possible to fully investigate these interre-
lationships here, having proper regard to the
principles of good housekeeping and some
understanding of the needs of the various
agents to flourish should enable them to be
kept under control (Pinniger 1994, 2001;
Sandwith and Stainton, 1991). For a general
review of biological agents of deterioration see
St George et al. (1954).
Fungi
Damage to free-standing objects from fungi
inside buildings has been known to occur in
museums and country houses where some
source of dampness has allowed locally high
humidity to occur or where ventilation is poor.
When it does occur it can quickly become
deep-rooted. Fungi constitute a large and
heterogeneous group of organisms within the
plant kingdom, all of which lack chlorophyll
and therefore cannot directly use energy from
sunlight. Fungi are more complex in organization
than bacteria but less so than mosses,
ferns and flowering plants. Those responsible
for deterioration of objects are mostly either
moulds or wood-destroying fungi. Wooddestroying
fungi are further discussed in
Chapter 7. The term mould, although not very
exactly defined in a biological sense, refers to
the small non-parasitic fungi and the term
mildew is generally used synonymously with
it.
Fungi are found widely distributed in soil,
water and air over much of the earth’s surface
with soil being the richest source. Fungi found
in the air are primarily present in the form of
spores. Fungi can utilize many different
organic substrates. Stachybotrys is a common
temperate climate form of fungus that attacks
paper and textiles and Pullularia is common
on paint films. Contact with soil is a good test
for the resistance of a material to degradation
and of the efficacy of fungicidal action.
However, it is equally clear that the presence
of soils (as may occur in old buildings and
outhouses) is to be avoided as a potential
source of deterioration.
Although wood-rotting fungi can be quite
large, the vast majority of fungi are small
enough that their characteristic structure can
be made out only with the aid of a microscope,
their largest parts being mostly less
than 5 mm across. A large fungal spore
measures about 20 μm in diameter, which is