Model 106-L Ozone Monitor Manual Rev. E
1
1. OZONE MONITOR INTRODUCTION
The 2B Technologies Model 106-L Ozone Monitor is designed to enable
accurate measurements of ozone in air over a wide dynamic range extending
from a few parts-per-billion by volume (ppb) to an upper limit of 10 parts-per-
million (ppm) based on the well established technique of absorption of
ultraviolet light at 254 nm. Note that throughout this manual and in the
instrument output, “ppb” (identical to “ppbv”) refers to parts-per-billion by
volume (not weight). The Ozone Monitor is light weight (4.2 lb., 1.9 kg.) and
has a low power consumption (
5.0 watt) relative to conventional instruments
and is therefore well suited for applications such as:
long-term monitoring at remote locations where power is highly
limited
monitoring and control of ozone in industrial settings
monitoring of exposure to individuals in the workplace
personal exposure monitoring for studies of health effects of air
pollutants
For aircraft flights where high temporal and spatial resolution is desired, the
Model 205 Ozone Monitor is recommended.
Theory of Operation
Absorption of UV light has long been used for measurements of atmospheric
ozone with high precision and accuracy. The ozone molecule has an
absorption maximum at 254 nm, coincident with the principal emission
wavelength of a low-pressure mercury lamp. Fortunately, few molecules found
at significant concentrations in the atmosphere absorb at this wavelength.
However, interferences, such as organic compounds containing aromatic rings,
can occur in highly polluted air.
Figure 1 is a schematic diagram of the Ozone Monitor. Ozone is measured
based on the attenuation of light passing through a 14-cm absorption cell fitted
with quartz windows. A low-pressure mercury lamp is located on one side of
the absorption cell, and a photodiode is located on the opposite side of the
absorption cell. The photodiode has a built-in interference filter centered on
254 nm, the principal wavelength of light emitted by the mercury lamp. An air
pump draws sample air into the instrument at a flow rate of approximately 1
L/min. A solenoid valve switches so as to alternately send this air directly into
the absorption cell or through an ozone scrubber and then into the absorption
cell. The intensity of light at the photodiode is measured in air that has passed
