1. What is the average concentration of carbon dioxide in the underground system? 2. What arrangements are made to extract carbon dioxide and other pollutants in the underground system? 3. What other air-born pollutants exist in the system and how are they dealt with? 4. How is carbon dioxide in the underground system monitored? 5. Which senior manager is responsible for these health and safety matters and what is his/her contact details?

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Our Ref:          FOI-0540-1819

Thank you for your request received on 31 May 2018 asking for information about carbon dioxide on the London Underground.
 
Your request has been considered in accordance with the requirements of the Environmental Information Regulations (EIR) and our information access policy. I can confirm we hold some of the information you require.
 
1.    What is the average concentration of carbon dioxide in the underground system?
 
London Underground do not routinely monitor carbon dioxide (CO2) levels in the underground network. Other than what people produce through respiration, CO2 is not generated from any other source. Ventilation systems are deemed to be adequate to keep CO2 levels within acceptable limits. The regulatory limits for CO2 are 5000 parts per million (ppm) for 8 hours time weighted equivalent or a short term exposure limit (15 minutes) of 15000ppm.
 
These exposure limits are published in the document below:
 
http://www.hse.gov.uk/pUbns/priced/eh40.pdf
 
On occasions CO2 monitoring has been undertaken to evaluate general air quality in the network. Please see the attached document:
 
CO2 measurements on the Victoria Line (passenger carriages) 2017
In the winter of 2017-2018 measurements were taken on the Victoria Line between Seven Sisters and Victoria station in the passenger cabins during peak flow periods. The results are in the attached excel spreadsheet. This was an informal exercise to get some background data. The average CO2 levels for the whole monitoring period were 1196 ppm (Aggregate of column F). Given the density of usage on this particular line these results are considered to be the higher end of CO2 concentrations on the network.
 
2.    What arrangements are made to extract carbon dioxide and other pollutants in the underground system?
 
Ventilation of the underground system is performed by two mechanisms. There are mechanical extract systems that draw air out of the system, normally mid tunnel. Intake air comes into the system via station and tunnel entrances. The other mechanism is performed by the movement of trains moving from underground to surface sections of lines. This has the effect of pushing and pulling large quantities of air out of the tunnels in a piston effect. Also when trains enter underground tunnels they draw in large quantities of fresh air behind them.
 
3.    What other air-born pollutants exist in the system and how are they dealt with?
 
Aside from CO2 which is generated by people the other major pollutant generated by London Undergrounds activities are particulates (dusts) which are generated from wheel, brake and rail wear and are composed mainly of iron. Removal of this is through cleaning and ventilation. In addition some of this dust becomes stuck to trains, particularly underneath and this is cleaned off regularly when the trains are serviced at maintenance depots.
 
Other pollutants are minor and coincidental to London Underground’s activities. The sources are largely road traffic and include oxides of nitrogen, carbon monoxide and volatile organic compounds.
 
4.    How is carbon dioxide in the underground system monitored?
 
CO2 is not routinely monitored. As stated above, other than what people produce through respiration, CO2 is not generated from any other source. When London Underground measure CO2 TSI Air Quality Meters are used, please see the link below:
 
http://www.tsi.com/iaq-calc-indoor-air-quality-meters-7545/
 
5. Which senior manager is responsible for these health and safety matters and what is his/her contact details?
 
Jill Collis is the Director of Health & Safety. Please note that in accordance with TfL’s obligations under Data Protection legislation we have not provide the requested contact details, as required by regulation 13 of the EIR. This is because disclosure of this personal data would be a breach of the legislation, specifically the first principle which requires all processing of personal data to be fair and lawful.
 
If a member of the public has any health or safety concerns then this can be raised via our Contact Centre. The contact details can be found on our website: https://tfl.gov.uk/help-and-contact/.
 
If this is not the information you are looking for, or if you are unable to access it for some reason, please feel free to contact me.
 
Please see the attached information sheet for details of your right to appeal.

Yours sincerely

Gemma Jacob
FOI Case Officer
FOI Case Management Team
General Counsel
Transport for London

foi@tfl.gov.uk

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