Shelter (in Place)
Shelter or "shelter in place" is a protective action with a wide range of applicability for radiation emergencies, chemical releases, earthquakes, flood/flash flood, storm,
pandemic and even for ongoing terrorist or criminal activity.
A nuclear power plant accident, a nuclear explosion or a dirty bomb are examples of radiation emergencies. If something like this happens, you may be asked to get
inside a building and take shelter for a period of time instead of leaving. The walls of the building can block much of the harmful radiation and reduce airborne levels
while the plume disperses. The best protection is provided by solidly constructed and reasonably airtight buildings.
In the context of nuclear emergency planning shelter is recommended if it is expected to avert at least 3 mSv of radiation dose.
(in the UK no authority can order the public the shelter without emergency powers being granted as they were during the Covid-19 crisis.)
How to do shelter well
The intention of shelter is to reduce the levels of contamination you and your family are breathing in. Just like you close the doors and windows of your house if there is a bad smell outside, such as a neighbour with a garden fire .
You are generally asked something along the lines of:
Close all doors and windows to minimise the risk of any possible contamination entering the building. Switch off fans, close ventilators and extinguish any fires to
prevent any possible contamination being drawn into the house e.g. via a chimney.
Keep domestic pets indoors to prevent them from bringing possible contamination into the house.
Do not attempt to collect children from school. Their teachers and the police will ensure they are looked after.
You will be much safer indoors. Please do not be tempted to evacuate the area unless advised to do so. If you try to leave before being instructed to evacuate you risk actually increasing your radiation dose (cars are not very good for the purpose of shielding) and blocking the road for the incoming emergency services.
Remain indoors until you are told by an official source that the danger has passed or you hear the all clear siren if there is one in your area.
Try not to use telephones to keep lines clear for use by emergency services.
Tune to your local radio station and listen for announcements telling you what to do.
If you can give shelter to anyone caught in the open, please do so.
An informative pictogram about sheltering in place as a response to a number of hazards including a nuclear release can be found on the
FEMA web site
or see Page 6 of the FEMA leaflet
It is worth noting that at least some of the advice available on American web-sites (including these two pictograms) is appropriate for households downwind of a nuclear bomb
which may be expected to produce far more "fallout", that is highly radioactive solids, than a credible accident at a nuclear licensed site. While there is probably no harm in
building a tent under the kitchen table it is probably an over-reaction to a radiation emergency
Food, Water & Medicines: it is safe to use food stored indoors, for example in homes or shops, medicines stored in their normal
packaging and mains tap water, unless told otherwise. However, you should wait for official guidance on using private water supplies,
consuming food stored outdoors, for example on open-air markets or stalls and harvesting fresh produce to eat, for example from a garden or allotment.
Food and Water Restrictions: If a radioactive release occurred, radioactive material could contaminate agricultural food
production (for example crops in fields and allotments) over a wide area. The Food Standards Agency advice will protect those people who
may consume this contaminated food on a regular basis and over a long period of time. The area covered by food advice is therefore
likely to be larger than the area in which evacuation or shelter is required.
Breaking shelter The NRPB (forerunner of the PHE and
the UK Health Security Agency stated that
significant problems can be reduced by advising individuals that short periods out of doors, for necessary activities will not, in many situations, result in high exposures"
(Documents of the NRPB, Volume 1, No 4 1990, Emergency Reference Levels of Dose for Early Countermeasures to Protect the Public).
PHE state that "the health and wellbeing of sheltered populations may be affected by restricted access to medical care or assistance. In such situations, consideration
should be given to supervised entry into the sheltered area by medical professionals and carers, or planned evacuation of these vulnerable groups
Preparing to shelter
There may be no notice of a nuclear emergency. You and your family should be ready to respond as soon as the alarm is raised. This means that you should all understand that
if you receive an alarm by whatever route (radio/TV news flash, social media from the Operator or Local Authority, telephone warning etc) you quickly go into your building and
take steps to reduce the exchange of air with the outside world (close doors and windows, switch off any fans and air conditioning etc).
It is unlikely that there will be disruption to utility supplies but you may need to shelter for up to two days. Would have have enough to eat and drink for this period?
You should have a Family Plan for what to do if some of you are inside the DEPZ and some of you are outside the DEPZ at the time of the alarm.
Schools and pre-schools will have plans to keep children under safe supervision. You should be aware of the plans at any settings that you use if either they or your home or both
are in a DEPZ. But what about family members who work outside a DEPZ but live in it?
You should know where the prior information leaflet is so that you can read it again and you should have a radio, TV or internet device allowing you to listen to local radio (and know how to tune to the local BBC channel).
Does anyone in your household take regular prescription medicines? Do you always have a few days supply in stock?
Ending Shelter in place
There is considerably more advice on the reasons to go in to shelter than there is to end it.
The PHE has this to say:
There are no predetermined radiological criteria for initiating withdrawal of sheltering and evacuation advice. In general terms, this advice should only be issued when these urgent
protective actions have achieved their desired effect by averting doses, or when their continued application will cause more harm than good in the broadest sense. When making decisions on
withdrawal of sheltering-in-place and evacuation advice, a large number of radiological and non-radiological factors need to be taken in to account, necessitating a pragmatic and flexible
approach. Radiological factors include: official confirmation that the release has stopped; monitoring data on ambient dose rates, ground deposition and surface contamination; and estimates
of effective doses integrated over a range of time periods.
Nonradiological factors include: wider health and social needs; caring for livestock; provision of resources for environmental monitoring, decontamination, medical services; and stakeholder
opinion. Withdrawal of sheltering-in-place and evacuation advice does not necessarily signify a return to normality. Evidence from previous radiation emergencies suggests that further
protective actions may be required ranging from some simple decontamination techniques to temporary or even permanent relocation''.
It is likely that people will be advised to stay in shelter, in increasing discomfort, while decision makers dither over how to quantify the spread of contamination and how to set limits on
low contaminations rates with no real effects on health. Meanwhile broadcast and social media will be muddying the waters with spurious expertise and outrage.
Public Health England notes on Shelter
Sheltering-in-place involves individuals going inside buildings, closing doors and windows, and turning off ventilation fans and air conditioning. The best protection is provided by
solidly constructed and reasonably airtight buildings. As a stand-alone action, sheltering-in-place can be used to provide protection against external radiation from airborne gases and
particles which have been deposited on the ground in inhabited areas. The dose reduction factors (DRF) for external gamma dose (derived solely on the basis of a literature review) are 0.15
for typical residential brick-built homes and 0.05 for multi-storey buildings (Bedwell et al, in preparation). Buildings can also slow down the rate of ingress of radioactive material that could be inhaled (Sheltering-in-place to reduce inhalation of airborne material is not unique to radiation emergencies since major chemical sites also have a similar approach). A Dose Reduction Factor of 0.6 (derived on the basis of a combination of modelling and literature review) should be assumed for inhalation dose to an individual sheltering during the entire passage of the plume, until both the indoor and outdoor air concentrations fall back down to (or close to) zero, with no opening of windows and doors to the external environment (and under such circumstances the DRF remains constant irrespective of the release duration). These generic, typical values can be applied to prospective assessments or retrospective assessments where scenario specific information is limited. Key factors affecting the effectiveness of sheltering-in-place include: the air permeability of a building used for shelter; the meteorological conditions; the particle size distribution; the effectiveness/timing of opening windows and doors; and the release duration, all of which could vary significantly from one scenario to another (or even within a single scenario). Some of these factors such as meteorological conditions are time dependent, and therefore the DRF may vary as a function
PHE state that “the health and wellbeing of sheltered populations may be affected by restricted access to medical care or assistance. In such situations, consideration should be
given to supervised entry into the sheltered area by medical professionals and carers, or planned evacuation of these vulnerable groups. Residents of hospitals and nursing homes can
face additional challenges, for example, sheltering-in-place without electrical power can be fatal for those dependent on modern technology such as ventilators. Therefore, if electrical
power is lost, evacuation of the vulnerable groups is likely to be essential in such situations. Similarly, specific support and advice should be provided to farmers needing to tend
livestock and those managing key infrastructure. Sheltering-in-place is not a long-term option and whilst it is potentially straightforward to implement, its use should ideally only be
planned to last hours, and, at most, 1 or 2 days. In order to minimise the anxiety and stress created by advice to shelter, it is important to ensure communication with those sheltering
is continuously maintained through appropriate communication channels. In particular, those sheltering-in-place for prolonged periods require reassurance that the advice has not changed
and that those from whom they may be separated (for example, children at school, partners at work) are being properly cared for.”
The science of Shelter
The intention of shelter is two fold:
1. It reduces the inhalation of radioactive dusts and gases by keeping them outside the building. See more detail on the page [[shelter science]].
2. It provides some shielding and some distance from any gamma emitters in the plume.
It is claimed that a solidly built and reasonably airtight UK house will reduce inhalation of particles by a factor of three and the direct gamma shine dose by a factor of ten.
However, it is thought to be ineffective for vapours and the protection only lasts for a few hours. Air exchange between the house and the outside, driven by temperature differences
and wind, allows the internal air to become contaminated in time.
The protection against external radiation offered by light constructions such as caravans is very small (no mention is made of the protection from inhalation offered by
caravans - a well draught-proofed one may perform well).