London Underground Air Quality

London Underground Air Quality

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Discussion

stevesingo

Original Poster:

4,848 posts

221 months

Tuesday 21st August 2018
quotequote all
I recently found myself in London and using the tube as a main form of transport.

What struck me was the pungent smell of brake linings when getting off the train.

The question is then, what sort of air quality management is happening underground?

It can't be good folks breathing that stuff during their commute, less so the workers who are subjected to a full shift of it.

Gary29

4,131 posts

98 months

Tuesday 21st August 2018
quotequote all
Definitely wouldn't want to work down there on a daily basis. I wonder if there are any cases of asbestosis caused by breathing in all that rubbish for years on end?

A lot of the air is moved by the piston effect of the trains running through the tunnels (so I read) and that's why you often get a huge waft of air being forced over you when you're going to escalators etc, due to the different air pressures below and above ground.

Interested to hear from people who know a lot more about this than I.

Yertis

18,015 posts

265 months

Tuesday 21st August 2018
quotequote all
stevesingo said:
I recently found myself in London and using the tube as a main form of transport.

What struck me was the pungent smell of brake linings when getting off the train.

The question is then, what sort of air quality management is happening underground?

It can't be good folks breathing that stuff during their commute, less so the workers who are subjected to a full shift of it.
I'm fairly sure they've stopped using asbestos in the brake linings. That pungent smell you refer to is a lot less 'acrid' (for want of a better word) than it used to be. Which is a shame, because I quite liked it – the smell of London.

I agree probably not good to breathe it all day everyday.

V8 Fettler

7,019 posts

131 months

Tuesday 21st August 2018
quotequote all
Assuming all the old asbestos dust has been removed, the biggest airborne pollutants are probably fine metallic particles from the rails/wheels and ozone from "sparking" (technical term).

Ye olde smoking carriages on ye olde underground in the previous century were an ordeal, even for committed smokers.


NDA

21,479 posts

224 months

Tuesday 21st August 2018
quotequote all
V8 Fettler said:
Ye olde smoking carriages on ye olde underground in the previous century were an ordeal, even for committed smokers.
Yes indeed. I smoked at the time and was always slightly irritated that sometimes a finished cigarette would slip between the wooden grooves on the escalators as you were putting it out (stepping on it).

It never occurred to the younger me how odd this would now be - or what a massive fire risk it was.

My grown up kids are always amazed when they see movies that show people smoking on trains, in offices and restaurants.

ukaskew

10,642 posts

220 months

Tuesday 21st August 2018
quotequote all
I'm always amazed at how dirty I am after a day in London, black snot is real! Oddly enough the only other city I spend a lot of time in (New York) doesn't give me the same feeling of grubiness.

The air quality difference is certainly most noticeable on the underground, and again it's not nearly as bad on the subway.

valiant

10,064 posts

159 months

Tuesday 21st August 2018
quotequote all
stevesingo said:
I recently found myself in London and using the tube as a main form of transport.

What struck me was the pungent smell of brake linings when getting off the train.

The question is then, what sort of air quality management is happening underground?

It can't be good folks breathing that stuff during their commute, less so the workers who are subjected to a full shift of it.
Try spending your working day down there...

What line were you using? Modern train stock uses a combination of regenerative, rheostatic and friction brakes which helps keep brake dust down to minimal levels (friction brakes will apply for the final few metres, usually the train is doing less than 8mph. However, if a particular powered car has a traction fault then all the braking in that car will be friction only, noticeable by a pungent burning smell where the friction brakes are working a lot harder than normal).

You also get the 'piston effect' where air is pushed in front of a train as it speeds along picking up crap and dumping it when the train stops usually in a platform. This can be exacerbated by the train barrelling along behind but it is mitigated by the pit you see in the platform between the tracks (people think it's a suicide pit but its primary purpose is air flow management) where air pushed by the train behind can be pushed under the train stationary in the platform.

Most of the crap you're breathing in is a combination of metal filings (steel wheel on steel track), small amount of brake dust, crap from outside getting sucked in and a lot of dead skin from your fellow commuters. It is monitored VERY closely (bit of a hot topic with staff at the moment). All measurements (carried out by an independent company) are well within government health guidelines (so they tell us!). There is also a program of tunnel cleaning that is regularly carried out with teams of blokes looking like ghostbusters hoovering and cleaning the tunnels (unfortunately the Hoover train project was cancelled) plus more high tech solutions in hotspots like special paints on tunnel walls that cause the dust to stick to it.

Air is probably a lot worse walking down a busy high street.


Edited by valiant on Tuesday 21st August 19:15

stevesingo

Original Poster:

4,848 posts

221 months

Tuesday 21st August 2018
quotequote all
Mainly the Central line with a little Circle line.

You could see a haze through the light at times.

EdJ

1,284 posts

194 months

Tuesday 21st August 2018
quotequote all
valiant said:
Try spending your working day down there...

What line were you using? Modern train stock uses a combination of regenerative, rheostatic and friction brakes which helps keep brake dust down to minimal levels (friction brakes will apply for the final few metres, usually the train is doing less than 8mph. However, if a particular powered car has a traction fault then all the braking in that car will be friction only, noticeable by a pungent burning smell where the friction brakes are working a lot harder than normal).

You also get the 'piston effect' where air is pushed in front of a train as it speeds along picking up crap and dumping it when the train stops usually in a platform. This can be exacerbated by the train barrelling along behind but it is mitigated by the pit you see in the platform between the tracks (people think it's a suicide pit but its primary purpose is air flow management) where air pushed by the train behind can be pushed under the train stationary in the platform.

Most of the crap you're breathing in is a combination of metal filings (steel wheel on steel track), small amount of brake dust, crap from outside getting sucked in and a lot of dead skin from your fellow commuters. It is monitored VERY closely (bit of a hot topic with staff at the moment). All measurements (carried out by an independent company) are well within government health guidelines (so they tell us!). There is also a program of tunnel cleaning that is regularly carried out with teams of blokes looking like ghostbusters hoovering and cleaning the tunnels (unfortunately the Hoover train project was cancelled) plus more high tech solutions in hotspots like special paints on tunnel walls that cause the dust to stick to it.

Air is probably a lot worse walking down a busy high street.


Edited by valiant on Tuesday 21st August 19:15
Interesting post - thanks.

valiant

10,064 posts

159 months

Tuesday 21st August 2018
quotequote all
Ahh, the Central line. That would explain it.

The 92 Stock has 'questionable' traction units where reliability is not the best. It is a common fault for a traction 'package' to drop out which means no motors in that car and also no rheostatic brakes. Also, if a driver has to perform an emergency brake - it is all done with friction brakes and can produce a fair bit if brake dust. If this was done a few trains before yours then the effect would still be noticeable. I once closed down London Bridge as I lost my door closed visual coming into the platform, slammed on the brakes and the dust set of the fire alarms - whoops! (It was only during the morning peak so only a few tens of thousand of commuters were inconvenienced...whistle )

Drivers can easily fix it but it is preferred to do it at a terminus just in case something untoward happens (trains can be weird sometimes). Good news is that the Central line fleet is having something like £300m spent on them to extend their life and one of the jobs is replacing all the motors with more reliable power plants.

rs1952

5,247 posts

258 months

Tuesday 21st August 2018
quotequote all
stevesingo said:
Mainly the Central line with a little Circle line.

You could see a haze through the light at times.
The Circle Line is underground in name only - it runs very close to the surface (built on the "cut and cover" principle) and you run out into daylight between many of the stations. At Edgware Road for example the station is in daylight.

The central line also runs in the open air east of Stratford and west of Shepherd's Bush. Here's a (not very good) shot of a Central Line train trying to run down an HST diverted down the old GWR Birmingham Main Line near Ruislip in September 2017:




tim0409

4,354 posts

158 months

Tuesday 21st August 2018
quotequote all
valiant said:
There is also a program of tunnel cleaning that is regularly carried out with teams of blokes looking like ghostbusters hoovering and cleaning the tunnels
Edited by valiant on Tuesday 21st August 19:15
I watched a documentary recently where they followed the tunnel cleaners during a shift; they said they pick up a lot of fibres (from clothes), and the fibres differed from section to section or line; the more affluent the area/line the more wool, and the less affluent was more synthetic - fascinating if true.

megaphone

10,692 posts

250 months

Wednesday 22nd August 2018
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aeropilot

34,289 posts

226 months

Wednesday 22nd August 2018
quotequote all
valiant said:
Ahh, the Central line. That would explain it.

The 92 Stock has 'questionable' traction units where reliability is not the best.
Only seems like yesterday that the Central Line was running the 62 Stock...........mind you, I can still remember when the red 38 Stock was in regular use on some lines frown

I'm really glad that the end of my regular Central Line tube use is just around the corner.


coldel

7,731 posts

145 months

Wednesday 22nd August 2018
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Use the district line each day, not so bad as pretty much all the way from Richmond to South Ken is above ground. Actually isnt more of the Underground above ground than under it..?

Anyway, I am sure there are people who would never use it daily, much better to sit in the car in traffic for half an hour on the commute tongue out

iphonedyou

9,234 posts

156 months

Wednesday 22nd August 2018
quotequote all
Yertis said:
I'm fairly sure they've stopped using asbestos in the brake linings. That pungent smell you refer to is a lot less 'acrid' (for want of a better word) than it used to be. Which is a shame, because I quite liked it – the smell of London.

I agree probably not good to breathe it all day everyday.
Yeah, the main source of asbestos in tunnel is in (much of) the caulking between rings on older lines.

NickCQ

5,392 posts

95 months

Wednesday 22nd August 2018
quotequote all
NDA said:
Yes indeed. I smoked at the time and was always slightly irritated that sometimes a finished cigarette would slip between the wooden grooves on the escalators as you were putting it out (stepping on it).

It never occurred to the younger me how odd this would now be - or what a massive fire risk it was.
Exactly what caused the King's Cross fire, of course.

LeoSayer

7,299 posts

243 months

Wednesday 22nd August 2018
quotequote all
I travel 11 stops on the central line every day from east to west and have done so for over 20 years - around the time when the current rolling stock was introduced.

I rarely smell anything which could come from brake linings but when I do - it's very obvious.