Product Manual

Table Of Contents
GasAlertMaxXT II
User Manual
30
TWA Alarm
The time-weighted average (TWA) is a safety measure used to
determine accumulated averages of gases. An average is determined
using the Occupational Safety and Health Administration (OSHA)
method to ensure the worker leaves an area when the maximum
average is accumulated.
OSHA: The OSHA method is defined as a moving average that
accumulates over an 8-hour average. If the worker is in the field longer,
the oldest accumulated values (first hour) are replaced by the newest
values (ninth hour). This continues for the duration of the work shift until
the detector is deactivated.
1. Refer to Resetting Gas Alarm Setpoints
for factory alarm
setpoints.
2. Enter the TWA alarm setpoint for the H
2
S and the CO
sensor in the TWA Alarm (ppm) field. TWA is not appli-
cable to O
2
and LEL.
3. Enter a value (4-16 hours) in the TWA Period (hours)
field to define the duration of the moving average. For
more information, refer to TWA Period (hours)
.
STEL Alarm
The short term exposure limit (STEL) is the maximum permissible gas
concentration a worker can be safely exposed to for short periods of time
(5-15 minutes maximum).
Note
Standard factory alarm setpoints vary by region. Refer to
Resetting Gas Alarm Setpoints
for OSHA factory settings.
1. Refer to the applicable regulatory requirements in your
area for defining STEL alarm setpoints.
2. Enter the setpoint in the STEL Alarm (ppm) field.
3. After entering the STEL setpoint, the STEL interval value
(5-15 minutes) must be entered. Refer to STEL Interval
.