MSA Sirius Mode D'emploi page 84

VOC Response factors apply in the 0-500 ppm range. The
values in this table were obtained using dry bottled gases
at 25°C. The response factors may change at higher con-
centrations, different temperature and humidity conditions,
or with cleanliness of lamp. For increased accuracy at dif-
ferent ambient conditions or concentrations, determine a
custom response factor and enter it via the Response
Factor page; see Chapter 3, Selecting a Custom
Response Factor. These response factors are specific to
the energy of the lamp designated in the table. They are
not valid for instruments using PID bulbs at any other ener-
gy. Using these response factors with a lamp at any other
energy may critically compromise the instrument's ability
to detect organic compounds which can result in serious
personal injury or death.
Use of Sirius PID for detection of extremely toxic gases:
The system resolution limit of the Sirius PID in normal
mode (with a new, clean lamp) is approximately 0.1 ppm
isobutylene equivalent. Users must be aware of exposure
limit guidelines, such as TLV, for the target analyte. Do not
use the Sirius PID Detector if the exposure limit for the tar-
get analyte is below 0.1 ppm. Failure to follow this warning
can cause over-exposure, which can result in serious per-
sonal injury or death.
For any analyte, its exposure limit guideline can be recalculated in
terms of equivalent ppm isobutylene by dividing the exposure limit
guideline by the appropriate response factor.
Example: For butadiene (CAS 106-99-0), the recommended threshold
limit value (as TWA) is 1 ppm. Its response factor (10.6 eV lamp) is
0.69. The TLV for butadiene, in terms of equivalent ppm isobutylene is:
ppm ÷ 0.69 = 1.4 ppm isobutylene equivalent.
The Sirius PID Detector has a reproducibility of +2ppm
(+2000 ppb) or 10%, whichever is greater (see TABLE 7-10).
The user must account for this potential variation between
the displayed value and the actual concentration when set-
ting alarms and interpreting readings. Failure to comply with
this warning can cause over-exposure and result in serious
personal injury or death.
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