Frequently Asked Questions About Citizen Preparedness

The Department of Homeland Security has received a variety of questions about how to prepare for a terrorist attack. Below are responses to the most commonly asked questions.

Should I purchase gas masks for my family?

No.  The use of gas masks and hoods by the public during a chemical threat is not recommended due to legitimate safety concerns.  Improper use of masks and hoods as well as a false sense of security as to their effectiveness could pose a threat to public safety. For example, it is difficult to obtain a proper seal with the mask if you have facial hair such as a beard or long sideburns. Protective masks do not fit small children. There is at least one, recent documented instance overseas where improper use of a gas mask lead to civilian deaths.

Why is this information being shared with the public now?

The Federal Emergency Management Agency and other emergency preparedness organizations at the state and local level and in the private sector, have a long history of working to provide the public with information on how to prepare for disaster risks in order to reduce the potential loss of life and property that a disaster can produce. Earlier this week, the Department of Homeland Security highlighted some of the information that is available from FEMA, the Department of Health and Human Services, the Center for Disease Control, as well as private organizations, on citizen preparedness. This information was provided as guidance based upon existing threats facing the United States and represents the first of what will be a sustained long-term effort to achieve the Department's overall goal of ensuring Americans are as prepared as possible.

Should I stockpile Potassium Iodide or Cipro?

The Department of Homeland Security and the Centers for Disease Control and Prevention would like all citizens to work with their local health care professionals and state health departments for more information about their particular circumstances.

When should someone evacuate versus sheltering-in-place?

Local officials are the best source of information when determining whether to evacuate or shelter in place.  In the event of an emergency, individuals should listen to their radios and follow the directions of the emergency officials.  In general, sheltering-in-place is appropriate when conditions require that you seek immediate protection in your home, place of employment, school or other location when disaster strikes.  People should take steps to prepare in advance in case local officials direct you to evacuate. This includes having a disaster supply kit that is portable and can be taken with you.

Can you really create a safe room?

Studies have shown that taking steps to temporary seal off a room using common materials enhances the safety of a room against the impact of a chemical plume.  The temporary shelter created by a safe room definitely provides more protection than basic sheltering, i.e. going indoors, closing windows and doors and shutting off HVAC systems.

How long can a family stay in a sealed room?

The Federal Emergency Management Agency recommends that individuals allow ten square feet of floor space per person in order to provide sufficient air to prevent carbon dioxide build up for up to 5 hours. Many chemical releases would be diluted within a few hours, so the direction to shelter-in-place would likely be made for a short time period while a chemical cloud dissipates. The need for long-term sheltering-in-place, e.g. having a three-day supply of food and water, is important for families preparing for emergencies when local authorities would tell them to stay put rather than evacuating.

Why does the government recommend duct tape and plastic sheeting?

In certain types of terrorist attacks, local authorities may suggest that you stay put or "shelter-in-place" in your home. Duct tape and plastic sheeting or even heavy duty trash bags can be used to create an airlock in a room to reduce the infiltration of chemical agents into an area. These materials are resistant to permeation from chemical agents and provide temporary shelter for you and your family for about five hours. Once the plume has passed, it is easy to remove these materials and exit.  

Is there a particular type (brand) of duct tape that citizens should buy?

The Federal Emergency Management Agency recommends using duct tape with a minimum thickness of 10 millimeters (0.01 in).  

What is the most effective type of plastic sheeting?

FEMA recommends using plastic sheeting with a thickness of 10 millimeters (0.01 in.).  For reference, commercially available sheeting is typically sold at 0.7, 1, 1.2, 1.5, 2, 2.5, 3, 4, 6 and 10 millimeters. But, keep in mind that any type of plastic sheeting, even heavy trash bags, can be better than nothing.  

Will shrink wrap plastic used for weatherproofing work?

FEMA does not recommend using shrink-wrap plastic. The double-faced tape to secure the shrink-wrap in place has not been tested with chemical agents.

Installing shrink wrap plastic would take more time than using plastic sheeting and duct tape due to the two steps required (adhesion to the frame using double sided tape and use of hair dryer to achieve a tight fit).

Do these precautions work?

The use of plastic sheeting and duct tape to reduce the permeability of chemicals into an area has been tested in several studies.

What is the science behind the recommendation to seal off rooms?

Duct tape was tested as part of a study on chemical protective clothing materials. In this study, it was concluded that duct tape provided at least a temporary seal against permeation by simulants of common chemical agents, including GB, VX, mustard and pesticides.  Depending on the chemical agent, duct tape resisted permeation for 3 ½ hours to more than 24 hours.  The study tested duct tape of 10 mil (0.01 in.) thickness.  Plastic sheeting was tested as part of a test using live chemical warfare agents conducted at the Chemical Defense Establishment in Porton Down, England in 1970.  Agents tested included H and VX.  Sheeting of various thickness was tested, including 2.5 millimeters (0.0025 in.), 4 millimeters (0.004 in.), 10 millimeters (0.01 in.) and 20 millimeters (0.02 in.).  

Is using wet towels over your mouth or at the bottom of doors and windows effective?

You should cover your mouth and nose while seeking shelter, but it should not be relied on as a safety measure in place of getting to shelter immediately.   In studies, using a dry folded handkerchief was the most effective filter.  Using wet material such as a towel or handkerchief actually reduced the effectiveness or filtering from vapors.  In addition, wet materials are more difficult to breathe through.  Placing a wet towel at the bottom of a door or window provides no protection against vapors entering a room.

Why do you shelter above ground for a chemical and biological attack vs. below ground for a radiological or nuclear attack?

In a chemical attack, the contaminants are typically distributed in an aerosol that is heavier than air.  As such, it will settle to the ground. The more shielding, distance and time you can take advantage of after a nuclear attack, the less exposure you will face. Sheltering below ground provides additional shielding protection from nuclear fallout through the earth that surrounds the underground shelter area.  The additional distance from the blast of a nuclear weapon provided by being below ground also offers an increased level of protection.