What if the cylinders are in a room with hoods that run constantly?
Just asking how this would impact a leak. If the tanks are next to the
hood does this remediate the situation itself?

Thanks in advance!

-Eric Goff

On 3/13/19, Monona Rossol
<0000030664c37427-dmarc-request**At_Symbol_Here**lists.princeton.edu> wrote:
> Best advice is:
>
> The sensor should be placed near the most probablelocation for a gas leak.
> The gas density and molecular weight are not very crucial for sensor
> placement, because all those gases, if released at room temperature will
> disperse in all directions about evenly unless is the release is so massive
> in volume that mixing with air is not occurring because the release is
> displacing room air in the vicinity of leak.
> Conversely, every one of those gases will head straight for the floor if
> they are under pressure and expand during release which makes them
> significantly cold and dense.  Once they reach room temperature, they will
> all will disperse in all directions.
> So placement is more dependent on 2) the temperature of the gas release with
> respect to the temperature of the air in the room  and 2) the size of the
> expected release.  For slow, small leaks, placing the sensor close to the
> source is best because no matter what the gas is, it will quickly come to
> room temperature, mix with air, and begin the processes of dispersing evenly
> throughout the room without respect to the weight of the gas with respect to
> air.
> May sound counter intuitive, but check it out. 'Tis so.
>  If you isolate a bottle of air for 10,000 years and don't disturb it, will
> the heavier molecules be more concentrated toward the bottom of the bottle?
>  And where are those very heavy chlorofluoro hydrocarbon propellant gases
> today?   Once you have the  the answers to those questions and the technical
> reasons for the answers, all the rest falls into place.
>
> Monona Rossol
>
>
>
>
>
> -----Original Message-----
> From: Mark Bachrach <markbachrach2015**At_Symbol_Here**U.NORTHWESTERN.EDU>
> To: DCHAS-L <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
> Sent: Tue, Mar 12, 2019 10:02 am
> Subject: Re: [DCHAS-L] Laboratory Gas Detection
>
> From our O2 alarm policy currently making its way through our policy
> committee:
> 1.     Oxygen sensors/detectors with low and high-level alarmswill be
> located in areas that present a potential asphyxiation hazard due tothe
> presence of manifolded or central liquid nitrogen or other
> asphyxiantgases.2.     Before any large volume container of compressed gas
> orcryogenic liquid is used, Environmental Health andSafety must be consulted
> to determine the need for oxygen detectors and oxygendepletion alarms.
> Environmental Health and Safety will perform the worst-casescenario
> calculation assuming the entire volume of container contents arereleased.
> If the final oxygenconcentration is lower than 18%, oxygen sensors and
> alarms should be placed. Thecalculation to be used is: Final O2
> concentration = 20.9 - 20.9*(Vgas/Vroom)whereVgas = volume gas released in
> cubic meters Vroom = room volume in cubic meters
> |  Liquid  |  Gas  |
> |  1L Liquid Nitrogen  |  0.694 m3 Nitrogen Gas  |
> |  1L Liquid Helium  |  0.757 m3 Helium Gas  |
> |  1L Liquid Argon  |  0.847 m3 Argon Gas  |
>
>  3.     Oxygen depletion alarms should not only sound locally. Allalarms
> should be tied into the Facilities Operations building alarm system.
> 4.     The placement of the sensors should also be determinedby EH&S,
> depending on the nature of the gas.
> |  Gases  |  Gas Density  |  Sensor Placement  |
> |  Argon, Heavy Hydrocarbons  |  Greater than air  |  Closer to the ground
> |
> |  Hydrogen, Helium, Methane  |  Less than air  |  Near the ceiling  |
> |  Carbon Monoxide, Nitrogen  |  Similar to air  |  At or near breathing
> level (4 to 6 ft. from the floor)  |
>
> The sensor should be placed near the most probablelocation for a gas leak.
> Whenever possible, the read-out panel or a strobeshould be placed in a safe
> area outside the room. The alarm must be audibleboth by the location of the
> read-out panel and by the sensor.
>
> On Tue, Mar 12, 2019 at 9:49 AM Stephen Beaton <Steve.Beaton**At_Symbol_Here**dal.ca> wrote:
>
> Hi all, I am researching best practice for fixed gas detection in
> laboratories in the university setting.  There are certainly a number of
> variables to consider. Does anyone have guidelines/ standards/
> decision-trees to establish whether detectors for flammable,
> oxygen-depleting and toxic gases are required in the laboratory? Thanks in
> advanceSteve Stephen Beaton, MSc, CHO, CRSP
> Chemical Safety Manager
>
> Environmental Health and Safety Office
> 902.494.1934 | steve.beaton**At_Symbol_Here**dal.ca
> DALHOUSIE UNIVERSITY  ---For more information about the DCHAS-L e-mail list,
> contact the Divisional membership chair at membership**At_Symbol_Here**dchas.orgFollow us on
> Twitter **At_Symbol_Here**acsdchas
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--
Best Regards,

-Eric

Eric W. Goff
Chemistry Educator