Evacuate or Shelter in place?

Taking Decisions about Evacuation during a Chemical Incident

From a Business Continuity or Emergency Planning perspective is it better to evacuate people in the vicinity of a serious chemical fire or should they remain where they are?

A study* comparing the health outcomes in sheltered and evacuated populations after a chemical fire suggests that there are health advantages in people sheltering rather than evacuating. The study is published in the BMJ and was based on a real incident in 1999. It involved collaboration between public health staff at a local health authority and national health experts (now at Bristol University and the Health Protection Agency).

In the event of a serious chemical incident where the public may be exposed to smoke from a fire, two main options of protective action exist - sheltering or evacuation. The prevailing expert view is to shelter, based largely on experimental and modelling studies.

This new study published in the British Medical Journal looks at a typical business continuity challenge, a fire started in a factory manufacturing plastic goods in southwest England. The factory was situated on an industrial estate adjoining a large residential area.

The initial response of the emergency services was to begin evacuating residents from their homes to a nearby leisure centre. This decision was subsequently reviewed and residents were advised to stay inside their homes and shelter. The resultant partial evacuation offered a rare opportunity to compare the relative health protection offered by these two modes of intervention.

A postal questionnaire survey was carried out on residents in the affected area and compared the health outcomes among the people evacuated (one third) and sheltered (two thirds).

In the two groups of residents similarly exposed to smoke plume from the chemical incident, the survey showed that evacuation did not confer any additional health benefit over sheltering. If anything, evacuated residents seemed to have more ill health effects soon after the incident than sheltered residents, although the difference did not seem to persist beyond two weeks.

Although the study has its limitations, it is a comparative study based on a real incident. The results reinforce the prevailing expert view that favours sheltering over evacuation as a response to protect populations exposed to chemical air pollution incidents. It is consistent with UK policy and practice in dealing with emergencies.

* Kinra S, Lewendon G, Nelder R, Herriott N, Mohan R, Hort M, Harrison S and Murray V, (2005). Evacuation decisions in a chemical air pollution incident: cross-sectional survey. BMJ, 330, 1471-1474.


For some time the evidence has been mounting for the benefits of 'Shelter in Place' (SiP) as opposed to evacuation for incidents of this type.

The latest Expert advice from Government currently recommends the value of SiP as a viable and effective alternative to evacuation for the management of local incidents based on, real life experience gained under a variety of circumstances. Currently, there is a belief that, on balance, for many types of incidents the difficulties of a even a minor evacuation expose those in the affected area to greater health risks than SiP.

The issue that this raises for those working in the BC arena is twofold, firstly, understanding your local risks, and secondly, ensuring that your planning is connected with that of the Local Authority and Emergency Services and that the decision to Shelter in Place can be effectively communicated to those on-site, particularly as employees and visitors may be anxious, or even panic when faced with the reality of an incident.

Potential Third Party risks, such as a Plastics or Chemical Factory in the general vicinity of your site/s should feature in the risk assessment/BIA of the BCP highlighting the location and type of facility, along with any other details that may be needed quickly in the wake of an incident. Local liaison is vital too, discuss the local plan for the management of any incident and ensure that there is a clear connection between YOUR response and that of the Emergency Services. Local Authorities should be able to provide detailed advice, and facilitate discussions with other services such as the Local Fire Service and Police should additional detail or measures be needed as there may be specific measures that need to be introduced such as turning off Air Conditioning Systems, which could compromise the benefits of SiP.

Remember though that plans can change and it is important to check back regularly to ensure your planning is still in tune with your local partners. It also pays to check quickly exactly what you are dealing with especially in built up areas and City Centres where the source may not be immediately clear.



If you have any comments on this article or would like to find out more about the work of the Continuity Forum please contact Sara McKenna or Russell at the Continuity Forum directly on 020 8993 1599 or info@continuityforum.org