The TERC ozonometer uses pure rubber thread, which develops
cracks very quickly in the presence of ozone. The thread is placed
in a mechanical arrangement such that the rate at which a pointer
rotates is proportional to the rubber deterioration which in turn
is proportional to the ozone concentration.
The TERC ozonometer can be used to measure concentrations of ozone
from 20 to 2000 parts per billion (ppb). The EPA limit above which
the air is declared unhealthy is 120 ppb averaged over one hour.
Our device is based on an ozonometer designed by J. R. Beatty
and A. E. Juve at the B. F. Goodrich Research Center in Brecksville,
Ohio, in 1954. Beatty and Juve used the fact that the presence
of ozone in air causes deterioration of rubber. The deterioration
takes place in the form of small cracks in the rubber. The rate
at which the cracks appear and lengthen is proportional to the
amount of ozone in the air. The figure below represents a magnified
view of stretched natural rubber golf ball thread before and after
exposure to ozone.
If you are interested is securing some untreated rubber thread, please contact Stephen Bannasch at Stephen@concord.org.
Rubber-thread Ozononmeter, large view
Building the Ozonometer
Materials
Tropospheric Ozone Index
Smogwatch Index