MSA altair 5, Руководство по эксплуатации, Страница: 19 / 221

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MSA DESCRIPTION
ALTAIR 5 - Operating Manual
19
2.4.4 Time Weighted Average (TWA page)
WARNING
If the TWA alarm activates, leave the contaminated area immediately; the
ambient gas concentration has reached the preset TWA alarm level.
Failure to follow this warning will cause over-exposure to toxic gases and
persons relying on this product for their safety could sustain serious
personal injury or death.
This page shows the average exposure since the instrument was turned
ON or since the TWA reading was reset. When the amount of gas detected
is greater than the eight-hour TWA limit:
Monochrome display Color display
TWA
•
Alarm sounds,
•
Alarm LEDs flash
•
“
TWA ALARM
” message flashes.
To reset the TWA:
(1) Access the TWA page.
(2) Press
the button.
The TWA alarm is calculated over an eight-hour exposure.
TWA calculation examples:
1-hour exposure of 50 ppm:
(1 hour x 50 ppm) + (7 hours x 0 ppm)
8 hours
= 6.25 ppm
4-hour exposure of 50 ppm and 4-hour exposure of 100 ppm:
(4 hours x 50 ppm) + (4 hours x 100 ppm)
8 hours
= 75 ppm
12-hour exposure of 100 ppm:
(12 hours x 100 ppm)
8 hours
= 150 ppm