Ozone generators

Lydia C. Egunnike <l.egunnike [at] snark__slq__qld__gov__au> writes

>Our air-conditioning contractors are investigating the possibility
>of installing ozone generators throughout the Library a/c system. It
>is envisaged that the generators will reduce the problems we are
>presently experiencing with mould outbreaks in the ducting. We have
>been assured that the level of ozone generated will be very small
>(0.02-0-04 ppm). However, I am still concerned at the possible
>adverse effects this may have on our collections.

I must point out a few considerations in response to Lydia
Egunnike's email on building ozone generators into her libraries'
air conditioning,

First, she states that 0.02-0-04 ppm is the ozone concentration
which will be generated.  From this alone it is not possible to know
how much ozone will actually be delivered to the collections. If we
assume typical losses from air conditioning, this could be from
nearly complete removal to only 20-30% removal.

Second, if ozone generation is going to be a low-level continuous
mold abatement operation in the air conditioning system, 0.02-0-04
ppm will be the 24-hour average dose delivered, adjusted for wall
losses and filtration (again from 95+% to 20-30%.) I should point
out that high outdoor levels of ozone are usually reported as the
peak 1 hour average.  While these 1 hour averages may be 10 times
higher than the levels generated within this air conditioning
system, it is nearly the same as the 24-hour summer average found in
the outdoor air of a city like Los Angeles.  Thus, if the intake air
of this design is chemically filtered, then ozonated, even if the
return air is re-filtered, 70% may make it to the collections. So we
are substituting one source of ozone for another and deriving no
benefit.

Third, most of the recommended levels of ozone exposure in the past
have been near the 0.001 ppm level. The only way a system like this
could work without introducing added risks to the collection is to
chemically filter the air just after the ozonation step.

If anyone is contemplating this kind of step in the future, they may
wish to check what CoOL has to say about this subject as well as
look into the warnings posted at
<URL:http://www.airpurifiers.com/ozone.htm>.  This is a commercial
site which  provides health warning links to the American Lung
Association, Health Canada, (the USA) Federal Trade Commission, and
(the USA) Environmental Protection Agency.  I would also strongly
suggest that one write to <purafil [at] purafil__com"> and ask them
whether or not long-term indoor ozone generation might reduce the
life expectancy of common chemical filter media types.

J. Druzik
Senior Scientist
The Getty Conservation Institute

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                  Conservation DistList Instance 12:77
                 Distributed: Wednesday, March 31, 1999
                       Message Id: cdl-12-77-003
                                  ***