[labnetwork] Question: use of gas alarm logic to prevent building evacuations on silane bottle changes...

[Keith Bradshaw]

With our Honeywell system, we put the sensor into overide mode for a time we
set and do the bottle work.  If we do not reset the sensor to alarmed, it
does so automatically after a timeout and flashes a blue light tower to let
us know the sensor is back on line.

Keith Bradshaw
Garland Texas

On Thu, May 5, 2011 at 7:44 PM, Ian Harvey <IRHarvey at eng.utah.edu> wrote:

> Dear Labnetwork,
>
> *Question:*
> How to prevent spurious gas/silane alarms (e.g., from cylinder change
> burps) from unnecessarily evacuating an entire building?
>
> *Background:*
> We recently had a very brief burst/decay of silane associated with the
> removal of the dust cap in preparation for installing a new silane cylinder.
> The burst was captured by our gas alarm as a single "spike" that exceeded
> the level-2 alarm threshold (10 PPM) for 3 seconds and decayed back to below
> level 1 (5 PPM) after 12 seconds (peak was 19 PPM).  However, the fire alarm
> was triggered, the entire engineering building was evacuated for 20 minutes,
> and six fire trucks showed up.
>
> This cylinder was 13 months old, 1 month past its expiration date.  The
> cylinder was chained and strapped into position inside the gas cabinet when
> the dust cap was removed.  At present, we feel it is best to evacuate the
> building, since our old lab is in a B-class occupancy area.  However, in our
> new facility, our silane will be behind a 2 hr firewall in a special gas
> room, attached to the single-story fab wing and 50 yards from (but still
> attached to) the multi-story research tower.  We are looking for more robust
> system-level solutions limiting unnecessary evacuation of the research tower
> in our new facility.
>
> *Approaches:* Aside from procedural approaches like "Don't use expired
> cylinders", and "Open dust caps very slowly", has anyone attempted to use
> alarm logic in their HPM system, such as: "<<If>> the alarm originates in
> the gas box <<and>> room air sensor is below threshold...  or variations on
> timing between sense and decay to stage the triggering of different alarm
> levels??
>
> How do others handle this situation in your respective labs?
>
> Thank you in advance for your inputs!
>
> --Ian
>
>  ********************************************
> Ian R. Harvey, Ph.D.
> Associate Director, Utah nanofab
> College of Engineering / University of Utah
>
> Research Associate Professor
> Department of Mechanical Engineering
> Adjunct Associate Professor
> Department of Electrical & Computer Engineering
> 2232 MEB
>
> mail to suite 2110 MEB, 50 S. Central Campus Drive
> Salt Lake City, Utah   84112-9011
> 801/585-6162 (voicemail)
> 801/581-5676 (lab main number)
> www.nanofab.utah.edu
>
>
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