Time Weighted Average (Twa) (Figure 3-13); Warning - MSA Sirius Operating Manual

The STEL alarm is calculated over a 15-minute exposure. Calculation
examples are as follows:
• Assume the Detector has been running for at least 15 minutes:
• 15-minute exposure of 35 PPM:
(15 minutes x 35 PPM)
15 minutes
• 10-minute exposure of 35 PPM
5-minute exposure of 15 PPM:
(10 minutes x 35 PPM) + (5 minutes x 15 PPM) = 28 PPM
If the STEL alarm condition is reached while using the
instrument as a personal or area monitor, leave the contam-
inated area immediately; the ambient gas concentration has
reached the preset STEL alarm level. Failure to follow this
warning will cause over-exposure to toxic gases, which can
result in serious personal injury or death.

Time Weighted Average (TWA) (FIGURE 3-13)

Figure 3-13. Exposure Page with TWA Alarm
• The TWA flag will appear in the upper portion of the display to
show the average exposure since the instrument was turned ON or
the TWA reading was reset.
= 35 PPM
15 minutes

" WARNING

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