Date: Tue, 11 May 2010 07:43:28 -0400
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: Ben Ruekberg <bruekberg**At_Symbol_Here**CHM.URI.EDU>
Subject: Re: 3 re: Hg response
In-Reply-To: <5F804CF6-9F1C-491F-9253-08530F446101**At_Symbol_Here**>

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Not wishing to be disputatious concerning the hazards of mercury, nonetheless, I think before worrying about the saturation vapor pressure of mercury, I suspect that one should also consider the rate of evaporation of mercury as well.=A0 I don’t know what it is, but were it all that significant people would probably have to have been refilling McLoed gauges with some frequency.=A0 In fact, I don’t recall that ever being necessary, nor do I recall finding significant amounts of mercury in the Nitrogen traps of vacuum systems under normal circumstances.=A0 Given that most rooms have reasonable air exchange, I suspect that rooms seldom reach saturation.

To refer to the example of 5 mg of mercury reaching the saturation concentration of 15 mg m^-3, one would be dealing with a room with a volume of 1/3 m^3, an unusually small room.=A0 A 20’ X 20’ X 10’ room would hold (at saturation, with no air exchange) ~ 1.6 g of mercury, a mere drop, but if a drop of mercury evaporated at a significant rate an amount that might be noticeable.

What I am suggesting is that the rate of evaporation might be more important than the saturation vapor pressure and may reduce the hazard (at least for the short term) and that one might not need to be overly alarmed.

Thank you,


From: DCHAS-L Discussion List [mailto:DCHAS-L**At_Symbol_Here**LIST.UVM.EDU] On Behalf Of List Moderator
Sent: Tuesday, May 11, 2010 7:16 AM
To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
Subject: Re: [DCHAS-L] 3 re: Hg response

From: "Allan Astrup Jensen" <aaj**At_Symbol_Here**>

Date: May 11, 2010 5:26:29 AM EDT

Subject: RE: [DCHAS-L] 3 re: Hg response

Please, don’t underestimate the danger of mercury vapour!

Mercury vapour is dangerous, and it is difficult to clean up indoor spills completely. Even the 5 mg Hg from a crushed light bulb indoors can create dangerous air concentrations, as many publications have shown. The saturated air concentration at room temperature is about 15 mg Hg/m3. That concentration is 500 times higher than the TLV, and such exposures have resulted in serious intoxications.


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Allan Astrup Jensen 

Technical Vice President 

Secretariat for Metrology, Chemical analysis and Management Systems 

FORCE Technology, Br=F8ndby 

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