The Close the Door study

End date: 
Tuesday, 10 June, 2014
The Aim: 

To monitor the levels of pollution inside shops on a busy high street, and how this changes when doors are left open or closed during working hours.


The Participants: 

The study was proposed by the Close the Door Campaign; a non-profit group of volunteers campaigning to stop shops wasting energy by keeping their doors open when using heating or air-conditioning. The project was undertaken with the co-operation and assistance of:

  • The Wolford Shop,
  • Nespresso,
  • Austin Reed/Viyella Flagship store,
  • Charles Tyrwhitt,
  • New West End Company,
  • The Regent Street Association,
  • Imperial College London


The Method: 

Over a six week period, black carbon, PM2.5 and nitrogen dioxide (NO2) were measured inside and outside four shops with different door opening policies.

The shops were located within 50 metres of each other, on the same side of the street and with entrances directly onto the street. All shops were mechanically ventilated.

The location of each measuring instrument, both in and outside the retail units, was carefully chosen to make the best comparison between shops as well as between inside/outside levels for each shop. Diaries were kept by the shop staff detailing when doors were open and closed and the flow of customers.


The Results: 

Analysis of the monitoring results clearly showed that the PM2.5 levels within the shops operating a closed door policy were 60% lower than those recorded outside on the street.

For those shops with open doors, the levels recorded inside the shops were only 45% lower than the levels recorded outside the shop. The results obtained from the black carbon measurements were very similar to the PM2.5 results. The findings of this study clearly show that it is possible to reduce staff and customers air pollution exposure by simply closing the shop door to the street.

The reduction in NO2 levels achieved by closing the doors was 17%, however, due to limitations in the monitoring method, this was during working and non-working hours. It is likely that the reduction would have been similar to PM2.5 if only working hours were considered.


The Outcome: 

The project findings will be used as evidence to help persuade retailers to implement a ‘closed door’ policy in shops on busy streets. The business friendly Close the Door initiative is taking information on air pollution in the retail space to discussions with managers on the high street and chain retail/restaurant head offices to increase awareness and encourage a change of policy or behaviour.

Close the Door are also spreading the information at local level through a network of Councils and Local Authorities, Business Improvement Districts, community organisations from religious groups, to sixth form colleges and other institutions supplying retail staff.


Contact Details: 

Project Coordinator: Jeannie Dawkins