1. Radiological and Chemical Defense

It entails closing all household doors, windows and vents and taking immediate shelter in a readily accessible location that puts as much indoor air and/or radiation shielding-mass between the individual and the hazardous outside air, such as a basement or centrally located medium to small room, and trying to make it as airtight as possible by shutting off all ventilation/HVAC systems and extensively sealing the shelter's doors and windows from all outside air contaminants with damp towels, or if available, plastic sheeting and adhesive tape.^[1] Diagrams of what sheltering in place entails following a chemical, biological, radiological or nuclear (CBRN) threat, and how long it is advised to be done for, is provided by the U.S. Federal Emergency Management Agency-affiliated website Ready.gov.^[2][3]

Shelter-in-place effectiveness has been evaluated and experimental results show that proper sealing can make a substantial difference to a normal home shelter, finding it to be at least twice as effective against a host of airborne substances when compared against simply staying inside and not implementing the countermeasure, and in most airborne contaminant cases, it is usually much more effective, depending on the particle size of the substance in question.^[4][5][6] If the occupant's breathing is the only consumer of oxygen and producer of carbon dioxide in the room, then carbon dioxide levels would not begin to reach dangerous values until 3+ hours had passed, in most likely, 4-person home scenarios.^[4][7]

In the military, "Shelter-in-Place" is comparable to "buttoning up" and has proved life-saving in certain nuclear fallout instances.^[8]

The danger of radiation from radioactive precipitation/"fallout" decreases with time, as radioactivity decays exponentially with time, such that for each factor of seven increase in time, the radiation is reduced by a factor of ten. Creating the following 7-10 rule-of-thumb after a typical nuclear detonation while under the conditions that all fallout that will fall on the land has done so completely and no further deposition in the area will occur - After 7 hours, the average dose rate outside is reduced by a factor of ten; after 49(7x7) hours, it is reduced by a further factor of ten (to a value of 1/100th of the initial dose rate); after two weeks the radiation from the fallout will have reduced by a factor of 1000 compared to the initial level; and after 14 weeks the average dose rate will have reduced to 1/10,000th of the initial level.

If an individual finds themselves outside during an emergency that calls for shelter-in-place, then effective but low-tech decontamination is required before entering into the shelter.^[9]

The phrase "Shelter-in-place" has also erroneously been used, instead of the more accurate lockdown, to describe precautions to be taken by the public when violence has occurred or might occur (particularly in shootings) in the area and the perpetrator is believed to still be in the area but not apprehended. The public in the area is advised to carry out all the same tasks as a typical shelter-in-place but without the key step of sealing the shelter up to prevent outside air from circulating indoors, in this scenario people are simply urged to lockdown — stay indoors and "close, lock and stay away from external doors and windows."^[10][11]

2. Shooting and Bombing Incidents

In light of active shooter events and the panic that can ensue, a lockdown alert issued as "shelter in place," can also be implemented as a response to armed events, such as the 2014 Fort Hood shooting.^[12][13] Similarly a lockdown alert was likewise issued as a "Shelter-in-place" alert by the Massachusetts Emergency Management Agency over the cell phone Wireless Emergency Alerts service for local residents during the manhunt for the Boston Marathon bombing suspects.^[14]

3. Implementation

Residents of an affected community might be informed that shelter in place is being implemented through the news media, Emergency Alert System, Reverse 911, warning sirens or horns, National Oceanic and Atmospheric Administration weather reports, and announcements from vehicles equipped with public address systems. In the United States, facilities like nuclear power plants are required to be equipped with audio alert systems that can be heard within a 10-mile (16 km) radius.^[1]

Once a shelter in place is called, residents are expected to immediately go indoors, bring all children and animals with them, and to close and lock windows and doors. All ways in which outside materials may enter the shelter area should be eliminated, including closure of fireplace dampers, shutting off ventilation or climate control systems, and prepare an area for pets to eliminate waste that does not require allowing them outside. If told to do so via television or radio, those sheltering should seal their rooms with duct tape and plastic.^[1] Upon reaching shelter, those who were outside for a period of time seeking shelter after the shelter in place was called and who may have been exposed to chemical contaminants should remove all outer clothing, put it in a plastic bag, and wash with warm water.^[9] After an announcement that the shelter in place is over, residents should go outside and open all doors and windows to ventilate the shelter. Similar processes should be followed in cars, workplaces, or schools.^[1]

4. Carbon Dioxide Concerns

Sheltering in place is generally only used for a short period of time, typically a few, around 3, hours, this number is based upon assuming the occupant's breathing-produced carbon dioxide is the only consumer of oxygen in the airtight room, in which case, carbon dioxide levels would not begin to reach dangerous values until 3+ hours had passed, in all likely, 4-person family home, scenarios,^[4][15] before room ventilation that must produce a full room air change for the shelter to be deemed "recharged"/ready for another ~3 hours. However if the outdoor hazard persists, the "~3 hour" period can be extended if the occupants have an accurate Carbon dioxide sensor, however as these devices can fail for example during the Soyuz 29 spaceflight, the experiencing of a headache can serve as a symptom to unsafe levels, in this case these headaches signaled the crew that their carbon dioxide detector had failed to alert them to change the air purifiers/carbon dioxide scrubber. Normal CO₂ levels were 8.8 mm Hg; the levels had likely reached 62 mm Hg to cause the headaches.^[16]

If shelter occupants have a CO₂ air concentration sensor and the occupants feel the need to stay within their shelter as long as the room air can safely provide, an accurate sensor can thus be used to squeeze the maximum from what the room has to safely offer. For even longer periods it is necessary that they make some prior preparations before sheltering in place. Being equipped with common drain cleaner that contains sodium hydroxide("caustic soda") — which is an effective carbon dioxide scrubber, and can be employed in an improvised rebreather, along with self-contained oxygen candles or the more common welding Oxygen tanks, are the type of equipment necessary to safely extend the period of Shelter-in-place past the point were respiratory/capnograph CO₂ levels would normally be deemed unsafe. In the case of the latter two oxygen sources, both of which also have the added benefit of producing and maintaining a shelter positive pressure which keeps any shelter leaks, leaking out rather than leaking in, Positive pressure environments are routinely employed in the hospital setting where the biological agents found in normal outside air, and generally harmless, may prove fatal to a weak immunosuppressed individual. In radiological/fallout scenarios, if the shelter is airtight and carbon dioxide and body heat build up is thus a concern, shelter-in-place time can be extended with the aid of a DIY Kearny Air Pump once a room air change is required, the use of which would be preferable to simply opening or unsealing the improvised shelters door.^[17]

It is also important to state that the ~3 hour maximum safe shelter-in-place period is derived from assuming occupants are in a typical sized room and that their respiration is the only producer of CO₂ in the shelter/room, failure to communicate this latter part of the warning to citizens has resulted in deaths. For example in March 2003, three Israeli residents of Kafr Qassem, a mother and her two sons, died in their sleep after sealing the room in which they were sleeping against potential chemical or biological attack. They had lit a charcoal fire to keep warm, unwittingly following the same preparations in charcoal-burning suicide.^[18]

5. Cases

• On October 2009, authorities called a shelter in place in Contra Costa County, California, after a teenager committed suicide by mixing chemicals together. Three nearby residents who were affected by the fumes were treated at a hospital, and the shelter in place order was lifted after three hours.^[19]

• On August 6, 2012, a shelter in place warning was issued in Richmond, California, due to a refinery fire at the Chevron Richmond Refinery.^[20][21]

• On October 29, 2012, a shelter in place warning was issued in Louisville, Kentucky, after a train carrying hazardous chemicals was derailed near Dixie Highway and Katherine Station.^[22]

6. Example of a Shelter in Place Warning

KABC URGENT - IMMEDIATE BROADCAST REQUESTED SHELTER IN PLACE WARNING BY ORDER OF LOS ANGELES POLICE DEPARTMENT,CALTRANS AND CALIFORNIA HIGHWAY PATROL RELAYED BY LOS ANGELES POLICE DEPARTMENT 12:00 PM PST SAT DEC 20 2016 THE FOLLOWING MESSAGE IS TRANSMITTED AT THE REQUEST OF THE LOS ANGELES POLICE DEPARTMENT. THE LOS ANGELES POLICE DEPARTMENT ARE ASKING ALL RESIDENTS OF LOS ANGELES COUNTY TO STAY INDOORS. AT 12:00 PACIFIC STANDARD TIME A CAR ACCIDENT HAS OCCURRED ON INTERSTATE 5 OUTSIDE LOS ANGELES COUNTY. THIS MOTOR VEHICLE ACCIDENT INCLUDED A SEMI TRUCK CARRYING 5 TONS OF SULFURIC ACID AND TOXIC GAS. FIRE FROM ACID HAD RELEASED TOXIC GAS THAT IS IN THE AIR. THE DIRECTION THAT THE WIND PUSHED THE GAS INTO DOWNTOWN LOS ANGELES. SHELTER IN PLACE IS IN EFFECT WITHIN 5 MILES OF THIS AREA. PLEASE DO NOT GO OUTDOORS AND REMAIN AWAY FROM WINDOWS OR ANY OPEN DOORS. PLEASE STAY TUNED TO MEDIA OUTLETS FOR FURTHER INFORMATION.

KABC


URGENT - IMMEDIATE BROADCAST REQUESTED
SHELTER IN PLACE WARNING
BY ORDER OF LOS ANGELES POLICE DEPARTMENT,CALTRANS AND CALIFORNIA HIGHWAY PATROL
RELAYED BY LOS ANGELES POLICE DEPARTMENT
12:00 PM PST SAT DEC 20 2016

THE FOLLOWING MESSAGE IS TRANSMITTED AT THE REQUEST OF THE
LOS ANGELES POLICE DEPARTMENT.

THE LOS ANGELES POLICE DEPARTMENT ARE ASKING ALL RESIDENTS OF LOS ANGELES COUNTY TO STAY INDOORS. 
AT 12:00 PACIFIC STANDARD TIME A CAR ACCIDENT HAS OCCURRED ON INTERSTATE 5 OUTSIDE LOS ANGELES COUNTY.
THIS MOTOR VEHICLE ACCIDENT INCLUDED A SEMI TRUCK CARRYING 5 TONS OF SULFURIC ACID AND TOXIC GAS. FIRE FROM ACID HAD RELEASED TOXIC GAS THAT IS IN THE AIR. THE DIRECTION THAT THE WIND PUSHED THE GAS INTO DOWNTOWN LOS ANGELES. SHELTER IN PLACE IS IN EFFECT WITHIN 5 MILES OF THIS AREA. 
 


PLEASE DO NOT GO OUTDOORS AND REMAIN AWAY FROM WINDOWS OR ANY OPEN DOORS. 

PLEASE STAY TUNED TO MEDIA OUTLETS FOR FURTHER INFORMATION.