Settings that can cause false TWA alerts

Combining the ACGIH method and settings that allow devices to stay online for days at a time creates a condition where accumulated gas readings are never given a chance to reset. A false TWA alert will be triggered when gas readings inevitably cross the TWA alert threshold.

A false TWA gas alert could be triggered when the device:

  • Detects a gas naturally found in the air (most often: CO2)
  • Is set to ACGIH for its TWA method (this method divides the total gas readings over 4-16 hours, rather than the rolling 8-hour average the OSHA method uses)

A false TWA gas alert becomes more likely:

  • When the device has a TWA period that is shorter than a typical work shift
  • If the features “operational while charging” or “disable device power down” are enabled

How to avoid false alerts on a device

Power down devices while charging or between shifts.


  • If ACGIH is not a requirement in your region, change the TWA method to the rolling 8-hour method
  • When using the ACGIH method, allow the device to power down while charging or between shifts

    How to resolve TWA alerts on a device

NOTE: Once the device is in TWA alert, monitoring services have been contacted and will follow the company’s emergency response protocol to ensure the user is safe. For this reason, we do not recommend power cycling the device until after the alert is resolved.

  1. Wait until the LiveResponse light has stopped shining and the alert is resolved (for monitored devices).
  2. Power cycle the device.
  3. Have someone with access to Blackline Live review configuration settings (see Recommendations above).