Shelter in place

Shelter in place (also known as a Shelter In-Place Warning SAME code: SPW) is to seek safety within the building you already occupy, rather than to evacuate the area or seek a community emergency shelter. The American Red Cross says the warning is issued when "chemical, biological, or radiological contaminants may be released accidentally or intentionally into the environment." and you should "select a small, interior room, with no or few windows, and taking refuge there."

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. 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.

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. 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.

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