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Computed Gas Exposures

Computed Gas Exposures

Warning

To prevent possible personal injury, do not deactivate the detector during a work shift. TWA, STEL, and MAX readings reset when the detector is deactivated.

Table 8. Computed Gas Exposures
Gas Exposure Description

TWA (H2S and CO only)

Time-weighted average (TWA) based on accumulated exposure to toxic gases averaged over a workday according to OSHA method.

Default: OSHA 8 hour moving average.

User-defined: 4-16 hour moving average.

STEL (H2S and CO only)

Short-term exposure limit (STEL) to gas based on a 5-15 minute user-defined period.

Maximum* (peak)

Maximum (MAX) concentration encountered during work shift.

* For oxygen, it is the highest or the lowest concentration encountered.

Viewing and Clearing Gas Exposures

To view the TWA, STEL, and maximum (MAX) readings, press Gas alarm twice rapidly. The LCD first displays the current time and date.

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Then, the TWA gas exposures display.

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Next, the STEL gas exposures display

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Next, the MAX readings display

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Last, the CLEAR ALL readings screen displays.

To clear the TWA, STEL, and MAX exposure readings, press Gas alarm when the following screen displays.

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Warning

Follow all safety procedures as defined by your employer.

Deactivating the detector clears all readings. Confirm with your supervisor before clearing TWA and STEL alarms.

Gas Alarm Setpoints

The alarm setpoints trigger the gas alarms and are described Table 9

Table 9. Gas Alarm Setpoints

AlarmCondition
Low alarm

Toxics and combustibles: Ambient gas level above low alarm setpoint.

Oxygen: Ambient gas level may be set above or below 20.9% (or 20.8%).

High alarm

Toxics and combustibles: Ambient gas level above high alarm setpoint.

Oxygen: Ambient gas level may be set above or below 20.9% (or 20.8%).

TWA alarm

Toxic only: Accumulated value above the TWA alarm setpoint.

STEL alarm

Toxic only: Accumulated value above the STEL alarm setpoint.

Multi-gas alarm

Two or more gas alarm conditions simultaneously.

Resetting Gas Alarm Setpoints

Table 10. lists alarm setpoints as defined by Occupational Safety and Health Association (OSHA).

Note

Standard factory alarm setpoints vary by region.

Table 10. Sample Factory Alarm Setpoints

GasTWASTELLowHigh
O2N/AN/A 19.5% vol.23.5% vol.
LELN/AN/A 10% LEL 20% LEL
CO35 ppm50 ppm 35 ppm200 ppm
H2S10 ppm15 ppm 10 ppm15 ppm

Note

To disable an alarm, set the alarm setpoint to 0 (zero) in Fleet Manager II.

To change the factory-defined alarm setpoints, refer to the following in User Options:

Stopping a Gas Alarm

The low and high alarms stop when the ambient gas concentrations returns to a concentration below the low alarm setpoint.

Note

If alarms are set to latch, press Gas alarm to reset the alarms

The detector computes the TWA value based on OSHA standards and the STEL value based on a user-defined 5 to 15 minute interval. Refer to STEL Interval.

The TWA and STEL alarms can be stopped either by

Caution

Follow all safety procedures as defined by your employer. Confirm with your supervisor before clearing TWA and STEL alarms.

Sensor Alarm

The detector tests for missing or defective sensors during the startup self-test and continuously thereafter. If a sensor fails the self-test, Err displays above the gas type of the failed sensor. If a sensor fails, refer to Troubleshooting.

Pump Alarm

The pump draws air over the sensors continually. If the pump stops operating or becomes blocked, the detector activates the pump alarm.

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During a pump alarm, HIGH and Alarm display, and Alarm flashes.

Note

The pump alarm displays the same as a high alarm, except that Alarm flashes. Verify that a pump alarm is occurring before clearing the hose.

The pump alarm continues until the alarm is acknowledged by pressing Gas alarm.

1. Clear the blockage and press Gas alarm to acknowledge. If Force Block Test is enabled, the detector automatically launches a pump test to verify the pump is operating correctly.

2. If the pump test is successful, the detector returns to normal operation.

If the pump test is unsuccessful, refer to Troubleshooting for possible causes and solutions.

Low Battery Alarm

The detector tests the battery on activation and continuously thereafter. Battery power is continually displayed during normal operation. If the battery voltage is low, the detector activates the low battery alarm.

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The low battery alarm continues 10 minutes. If the battery voltage drops too low, the detector activates the automatic deactivation alarm.

Automatic Deactivation Alarm

If the battery is depleted below the minimum operating voltage, a sequence of ten sirens and alternating flashes activates with 1 second of silence in between. The sequence repeats seven times. The following screens displays and the detector deactivates.

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To charge the detector, refer to Charging the Battery