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[Jerome Malsack]

Subway fire in DC,  L'Enfant Plaza Metro Station   Arcing on the third rail  causing  Noxious gas.   

[Daniel Levi]

I am surprised about it creating noxious gases, arcing could create ozone I suppose.
We have a fair bit of third rail over here (even on long stretches of main line) and never had a problem with arcing causing noxious gases.

[Scott Holtzman]

I am surprised about it creating noxious gases, arcing could create ozone I suppose.
We have a fair bit of third rail over here (even on long stretches of main line) and never had a problem with arcing causing noxious gases.

The people were covered with some gooey black stuff on the late news.  That could be from the person that was stuck on the third rail.  It was not o^3

[Mac Kerr]

I am surprised about it creating noxious gases, arcing could create ozone I suppose.
We have a fair bit of third rail over here (even on long stretches of main line) and never had a problem with arcing causing noxious gases.

Arcing between 2 clean electrodes might only produce ozone, but subway power is covered in sludge from being under trains for years without ever being cleaned. Some other substance on the rail could burn and create any number of noxious gases.

Mac

[Scott Holtzman]

Arcing between 2 clean electrodes might only produce ozone, but subway power is covered in sludge from being under trains for years without ever being cleaned. Some other substance on the rail could burn and create any number of noxious gases.

Mac

And to be clear I was being obnoxious about the human remains.  Mac's explanation makes sense and is far less gross.  Quite a lot of people overcome,  84 admitted to hospital and 4 fatalities so nothing funny about the incident at all.  The NTSB report should be a good read. 

[Jerome Malsack]

Agreed on the NTSB report and if there is a finding of foreign substance around the rails causing the fumes.  Grease or oils who knows what is down in the floors between rails. 
  Obnoxious on the human remains may not be a far stretch with all the shootings that have made the news here also. 

[Jerome Malsack]

update on news.
http://www.wusa9.com/story/news/local/dc/2015/01/16/ntsb-releases-preliminary-report-on-metro-smoke/21877471/

http://www.ntsb.gov/investigations/AccidentReports/Pages/DCA15FR004_preliminary.aspx

With the metro sending a command to open the second breaker makes me wonder if this is the same breakers on the recall ? 

[Stephen Swaffer]

The metro trains run on a 750 V DC rail-each car has 1000 HP (typically)-so no the breakers can't be the ones on recall-not anywhere near big enough.

My guess is that the arcing event eventually melted enough metals to extinguish itself -although DC might have taken a rather large gap to stop  (anyone that has stick welded with both AC and DC knows a DC arc will stay established a lot easier).  But in order for workers to enter the tunnel, it had to be de-energized for safety.

I don't know what type of insulation was on the cables involved-but I have been cautioned by electrical inspectors to minimize the amount of URD (typical direct burial "Underground residential distribution") run inside a home since the insulation produces a toxic smoke when it burns. So it would not surprise me if the insulation on these cables produced a toxic smoke.

 

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