When will the MASH alarm be triggered?

Last updated 2/2/2026

Overview

Sashimi sensor's have a built in Motion and Sash Height (MASH) alarm designed to monitor sash height and user presence. The system triggers audio alarms in specific scenarios to ensure laboratory safety, maintain proper airflow, and conserve energy.

This guide details the two primary alarm scenarios.

Alarm Type 1: Safe Operating Height (Safety Alarm)

Purpose: To prevent airflow disruption and ensure the fume hood effectively draws harmful fumes away from the user.

Trigger Conditions: This alarm activates when the sash remains open beyond the safe limit for an extended period, regardless of whether a user is present.

• Height Condition: The sash is raised above or to the Max Safe Operating Height.

  • Note: This height is determined at installation. It is often visually indicated by the "sash stopper" (the mechanism that must be manually engaged to raise the sash further).

  • Note: The mash alarm is activated if the fume hood is open past Max Safe Operating Height.

• Time Condition: The sash remains in this position for longer than the Max Idle Time.

  • Default Max Idle Time Setting: Immediate

  • Configuration: This time limit can be adjusted by an administrator.

Why this matters: The sash should only be above the operating height, if needed, during equipment setup. Once setup is complete, the sash should be returned to the safe operating height according to widely-accepted occupational health safety standards. Leaving the sash fully open disrupts the aerodynamics of the hood, significantly reducing its ability to contain fumes and protect the user.

If during setup, you'd like to mute the sensor, press the button on Sashimi once. This will temporarily mute the sensor. For more details on muting the sensor, refer to this article.

Alarm Type 2: Unattended Sash (Energy Conservation)

Purpose: To act as a reminder to close the sash when the hood is not in use, preventing energy waste and improving general lab safety.

Trigger Conditions: This alarm activates only when the hood appears to be abandoned while left open.

• Height Condition: The sash is left open above the Minimum Closed Threshold.

  • Default Setting: 3 inches.

  • Configuration: This setting can be adjusted by an administrator.

• Time Condition: The sash has been left at this height for longer than the Unattended Time Limit.

  • Default Setting: 5 minutes.

  • Configuration: This setting can be adjusted by an administrator.

• Occupancy Condition: No user is detected by the occupancy sensor during this time window.

Why this matters: Fume hoods consume a significant amount of energy when left open. If no user is detected near the hood, the system assumes the sash was accidentally left open and triggers an alert to encourage closure.

A note on false positives: The occupancy sensor is currently tuned to high sensitivity to ensure it doesn't fail to detect a user working at the hood. While this may result in "false positives"—where motion is detected from the general vicinity rather than just directly in front of the sash—this approach is intentional. We prioritize safety by ensuring the system acts "over-sensitively" rather than risking a scenario where a user working quietly is not detected. We are actively refining these thresholds to a optimal balance between recognizing active users and ignoring passing traffic.

Quick Reference Table

Last updated 1/31/2026

Overview

Sashimi sensor's have a built in Motion and Sash Height (MASH) alarm designed to monitor sash height and user presence. The system triggers audio alarms in specific scenarios to ensure laboratory safety, maintain proper airflow, and conserve energy.

This guide details the two primary alarm scenarios.

Alarm Type 1: Safe Operating Height (Safety Alarm)

Purpose: To prevent airflow disruption and ensure the fume hood effectively draws harmful fumes away from the user.

Trigger Conditions: This alarm activates when the sash remains open beyond the safe limit for an extended period, regardless of whether a user is present.

• Height Condition: The sash is raised above or to the Max Safe Operating Height.

  • Note: This height is determined at installation. It is often visually indicated by the "sash stopper" (the mechanism that must be manually engaged to raise the sash further).

  • Note: The mash alarm is activated if the fume hood is open past Max Safe Operating Height.

• Time Condition: The sash remains in this position for longer than the Max Idle Time.

  • Default Max Idle Time: Immediate

  • Configuration: This time limit can be adjusted by an administrator.

Why this matters: The sash should only be above the operating height, if needed, during equipment setup. Once setup is complete, the sash should be returned to the safe operating height according to widely-accepted occupational health safety standards. Leaving the sash fully open disrupts the aerodynamics of the hood, significantly reducing its ability to contain fumes and protect the user.

If during setup, you'd like to mute the sensor, press the button on Sashimi once. This will temporarily mute the sensor. For more details on muting the sensor, refer to this article.

Alarm Type 2: Unattended Sash (Energy Conservation)

Purpose: To act as a reminder to close the sash when the hood is not in use, preventing energy waste and improving general lab safety.

Trigger Conditions: This alarm activates only when the hood appears to be abandoned while left open.

• Height Condition: The sash is left open above the Minimum Closed Threshold.

  • Default Setting: 3 inches.

  • Configuration: This setting can be adjusted by an administrator.

• Time Condition: The sash has been left at this height for longer than the Unattended Time Limit.

  • Default Setting: 5 minutes.

  • Configuration: This setting can be adjusted by an administrator.

• Occupancy Condition: No user is detected by the occupancy sensor during this time window.

Why this matters: Fume hoods consume a significant amount of energy when left open. If no user is detected near the hood, the system assumes the sash was accidentally left open and triggers an alert to encourage closure.

A note on false positives: The occupancy sensor is currently tuned to high sensitivity to ensure it doesn't fail to detect a user working at the hood. While this may result in "false positives"—where motion is detected from the general vicinity rather than just directly in front of the sash—this approach is intentional. We prioritize safety by ensuring the system acts "over-sensitively" rather than risking a scenario where a user working quietly is not detected. We are actively refining these thresholds to a optimal balance between recognizing active users and ignoring passing traffic.

Quick Reference Table