The ozone layer protects
humanity from the effects of ultraviolet rays, but ozone itself because of its
high capacity to react through its extra oxygen atom causes the need for ozone
resisting material to be used for ensuring the longevity of buildings.
Ozone is an oxidizing agent
that is very powerful; its power comes from the free oxygen atom that results
after atmospheric oxygen is converted into O3 . This
is the result of electrical discharge from lightning and other atmospheric
actions that produce electrical activity. This third atom of oxygen in ozone is
not very stable and usually last very long, but it is constantly looking to
link up with other atoms to achieve some stability. This is what causes the ill
effects of ozone. It degrades material that it comes into contact with it and
causes some sort of fading, as well as a loss in tensile strength, which
accelerates aging and thus a reduction in the value.
Ozone causes substantial
damage to rubber products, surface coatings, and polymers, all of which are
used extensively in the building industry. While inorganic materials remain
largely unaffected by ozone, its combination with sulfur dioxide
and nitrogen dioxide present in the atmosphere has a deleterious effect on
metals. For the same reason, the zinc that is contained in most paints causes
it to be vulnerable to ozone. Of all the metals, copper and tin seem to be most
vulnerable.
Ozone is formed as a result of
electrical discharge combining with the atmospheric oxygen, and this is a
situation that can be also largely prevalent in electrical equipment and
installations. The ozone that does get formed can affect the insulation of
wires and cause them to deteriorate, especially when the concentration of ozone
exceeds 20 percent. For this reason, standards have been developed for
insulation that will be resistant to such effects. This also includes the
insulating compounds that are used to join wires and cables.
Rubber seals and sealing
compounds used to weatherproof glazed windows are other building materials that
are affected by ozone. Ozone in combination with ultraviolet rays cause such
seals and compounds to become brittle and thus less effective in their
function. Natural rubber and PVC are very vulnerable to ozone, and their use
these days has become very limited in the building industry. Ozone gas attacks
the polymers of which these materials consist, causing cracks in them to grow
longer and deeper and, thus, complete degradation of the material. The
application of waxes to protect the surface of these materials has been known
to be effective, but these waxes are affected by heat and mechanical effects.
This has led to the development of EPDM, which has a high resistance to heat,
ozone, and UV rays, plus a resistance to color fading.
This has led to architects specifying their use for weatherproofing of windows
and around glass in glass facades.