Research and analysis

London Underground: technical overview of study into how air flows around the network

Overview of equipment used for a study conducted in June 2013 to increase our understanding of how air flows around the London Underground.

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Technical overview of the airflow study on the London Underground

This short film shows and explains the equipment used during the airflow study on the London Underground.

This relates to a study conducted in June 2013 by the Department for Transport, supported by London Underground and the British Transport Police.

A further short film providing more information about the study is also available.


Okay, so I’d like to demonstrate to you, one of the equipments we use in the air flow releases within London Underground. This consists of a bottle of gas, a regulator, a mass flow controller and a pipe which then releases the material from the top here.

We’re looking at more than one type of tracer material and the different type of material is released using this equipment. This equipment consists of a battery, an inverter, a hotplate, and actual tracer materials in that bottle there. It comes out that bottle, goes on to the hotplate. It then vaporises and this fan then blows the vapour out.

We then need to confirm that the release has behaved as we expect it to behave and the first step in doing this is using this device here called an anemometer. An anemometer uses ultrasonics to measure airflow past it and by using that equipment we get an initial indication that the airflow is proceeding as we expect it to.

The next step is to look and use a piece of equipment we have here, this is called a Miran. This uses a red light source, material comes in through the receptacle here. It goes in through a series of pipes along which that light source passes. Because the material we use absorbs light in a certain way, we then have a detector which monitors how that absorbance happens.

So by, by using this equipment we have a bit more detail about how much material is being released and where it is.

I just told you about the Miran which looks at one of the tracer materials we release and would like to show some other equipment that looks at the other tracer materials that we release. The first of which is called an IBAC, that, measures the number of particles and the fluorescence properties of those particles.

And then if we move on to this piece of equipment here, that consists of a series of, of bags which at different time points collect the material as released. The samples are then taken from these bags and analysed in the laboratory later on.

Published 17 June 2013