Tracking the Plume: Dodging the Toxic Cloud When Deciding to Bug-in or Bug-out, by B.H.

Someone just told you about the Boston Marathon bombing. You are combing the interwebs looking for more details and view several videos of explosions and subsequent swirling brownish smoke. What was in that smoke? Did anyone die from just that smoke? Was it cancerous? Was it filled with botulism? Mustard gas? Alpha particles from a dirty bomb?

While people either ran away from the explosion, sought cover, or were moving toward the explosion to help victims, most people probably did not worry about what was in that smoke. I, on the other hand, was primarily concerned about the smoke wondering if there were any contaminants in those bombs.

During Operation Iraqi Freedom (OIF) I was part of a unit called the Combined Joint Task Force, Consequence Management (CJTF-CM). Our basic job was to respond to Sadaam’s chemical or biological SCUD missiles by cordoning off and decontaminating the area hit. When I saw the bombing videos, a year’s worth of training came rushing back to my brain and after looking through the archives did not see much written on this topic and thought I would share my experiences and ideas.

The purpose of this article is to provide you with a very simplified decision aid, when you think or the news lets you know that a chemical, biological, radiological, or nuclear (CBRN) release occurred near you, your bug out location, or somewhere in between and you need to decide to bug in or bug out.

Before we begin, I will first define what I mean by “plume”. That brown cloud of dust from the marathon bombs contained particles that, at first, have no real shape and are amoeba-like. After a few seconds to minutes, though, that cloud of particles will move and form what is referred to as a plume. A simple way to visualize a plume is to look at an active smoke stack on a windy day. If there is no wind, the smoke tends to look like a large cloud. With some wind, however, it tends to take on a cone-like shape that expands up, down, left, and right as it elongates with the wind direction. This is the “plume”. Even if there is no wind, eventually, the smoke will move with air pressure vagaries associated with whatever terrain is in the area.

If the plume is contaminated with any CBRN agent, then it is probably something you should be concerned about because the longer you spend in the plume, protected or not, the greater the chance of serious injury or death. Not to mention, if you are in the plume, you are dragging whatever is in the plume with you to wherever you are going–you are now contaminated and spreading it! Understanding how a toxic plume moves is critical to staying safe and preventing further contamination.

Two skills and one piece of background knowledge are required for understanding how to avoid the plume: 1) being able to conduct an Intelligence Preparation of the Battle (IPB) and 2) predicting the weather. Also, knowing how officials will respond will impact your mobility, so having some background information about first-responder activity will help you when making your decision to stay or go.

Disclaimer: Tracking the plume is incredibly difficult to do, and my goal is to break it down into simple discrete steps that can be performed while under pressure. If an event occurs and you are in a position where you have to decide whether to bug out or bug in, I am confident that this article will help you make a sound, informed decision. Heck, we were willing to put our lives on the line during OIF using this technique. However, a toxic plume can be similar to a wild animal in that you are never 100% certain of anything, so please use caution and your best judgment.

Background Information

Anticipating how responders deal with a CBRN event will definitely affect your mobility, so it is important to anticipate and plan for their actions. Once a CBRN event occurs, the first thing responders will do is cordon the area, at least that is what we did when we trained for OIF. The purpose of this cordon is to prevent anyone from entering the immediate contaminated area. This area will be impassable to you. If this area lies in your area of operation (AO), you will not be going through it and must find another route. For the sake of this article, your AO is your house, where you commute to, your bug out location, and everywhere in between. According to the Center for Disease Control’s directions for first responders (index for type of agent is found here), the cordon area has a radius of .5 mile. It sounds small, but the man power required to cordon this area will take more than just your local police department. Not to mention the people trying to get out of that radius because they are contaminated and doing the Sarin-induced funky chicken. In other words, that immediate cordon area will be chaotic and dangerous. Once the area is cordoned, responders will begin attempting to decontaminate, while at the same time working downwind of the plume, in an area not yet touched by the toxic plume, but soon to be touched, to protect citizens. The typical advice we gave the Kuwaitis was seal all doors and windows with duct tape, grab gas masks, wear clothes with limited skin exposed, and wait until they heard the all clear siren. Here in the U.S., with the National Defense Authorization Act, I might imagine this would be perfect for martial law with similar directions to households. Obviously, a martial law type situation will dramatically hinder your ability to move. Luckily, this step will probably take a while, and if you move within the first four hours, odds are, you will avoid a martial law scenario. The man power to enforce such an action is tremendous; we had 1800 troops from all four branches of the U.S. military and five other countries, plus some large vehicles, and we were going to fall far short for anything sustainable. I guess I would say you have a little bit of time, but I am not sure I would push it. There are also competing priorities for responders. They must prevent people from entering the area, they must find people, clean them, then attempt to triage the injured. If weather conditions are favorable for CBRN agents, responders may actually try to decontaminate the terrain. During our training for OIF, we tried to avoid this at all cost because time, some wind, and rain make most agents disappear within a day or two. Why kill our own trying to clean when we can wait? Nonetheless, decontaminating terrain may occur, thus reducing your mobility. After initial cordon, responders may move about the contaminated area searching for survivors and decontaminating personnel and equipment.

All this adds up to a lot of people and large vehicles in the middle of your area of operation (AO) that are either trying to clean you (whether you like it or not), prevent you from moving where you want to go, or just getting in your way and reducing mobility to a crawl.

From what we practiced in OIF, we tried to get the cordon done in the first four hours and establish command and control with the first round of decontamination completed within eight hours. At 12 hours into the incident, we were prepared to hand over operations to a larger unit capable of sustainable decontamination operations. What this means for you is that, ideally, you want to make your decision and be moving well inside of the first four hours. After four hours, assume responders will have things generally under control and your mobility will be extremely limited.

Responders require assets– local or outsourced. The first of which will probably be water. Water and lots of it are critical to decontamination efforts. Medical treatment facilities will also be needed. We planned on overcrowding for Kuwait City hospital beds within the first four hours, so we knew we needed a field hospital. We also needed a command post (CP) to coordinate and maintain situational awareness. We had enough assets to set up a small, fully equipped CP, but we were only directing direct traffic, so to speak. If an event had occurred and we had cordoned the area, knew casualty counts, area of damage, agent used, et cetera., we would turn it over to Doha’s command at about 12 hours after the event. I mention this because first responders will use what they have on hand–local fire trucks, rivers, ponds, fire hydrants, anything capable of producing water. Plus they’ll use their small deployable CP on wheels or take over a nearby school, office building, or barn. Areas large enough for field hospitals that are dust-off capable (able to land a helicopter) will be obtained by responders. Think about the movie Contagion–schools and stadiums are perfect locations for a combination command post, field hospital, and decontamination site. Remember, responders going into the area need to be cleaned after coming out of the contaminated area and so do the vehicles. It is a fairly massive operation, which requires a few football fields of space with tens of thousands of gallons of water per day. Traffic into and out of this area will be closely guarded and controlled to prevent the spread of the contaminant.

Keep this information in mind for when I discuss your AO IPB.

Plume Intelligence Preparation of the Battle

The next part of IPB is to actually track the plume itself. What I present here is based on experience from OIF as well as guidance from online plume models such as ALOHA (you can download a free copy here), which is made by NOAA. It is really pretty cool, and I recommend playing with it. The model we used, that FEMA gave us during OIF, was very similar, although with less capability. (I used the model 10 years ago!) Basically, these models are on a computer; you enter the parameters, and it generates a multicolored teardrop looking plume, overlaid on a map of the area based on parameters like type of agent, size of incident, wind speed, and so forth.

Using a clear piece of plastic with some stiffness, like a transparency, cut out an 8 x 4 inch rectangle, assuming you are using a 1:24,000 scale map. I say rectangle because it has more surface area and thus is a safer geometric shape for tracking a plume. Outline the rectangle first with a marker, so it leaves a line around the edges. Draw a line in the middle of the rectangle down the long axis. At one end of the rectangle, where the middle line intersects the short edge of the rectangle, make a dot. This is your generic plume, a rectangle with a line down the middle long ways and a dot at one end. On a 1:24,000 map this equates to a 3-mile long by 1.5-mile wide area of plume. Now, according to the CDC website, this is too small of an area for a large Sarin-tipped missile. The CDC claims they would want to “protect” persons seven+ miles downwind for a 53 gallon spill, as if it were in a large missile. Given the average map size and the quickness a prepared person would want to leave (inside of four hours) a 3 x 1.5 mile rectangle is probably okay. Now remember, I did say PROBABLY. Ideally, you would want a rectangle 20 inches long (seven miles) by 8 inches wide (three miles) in keeping with CDC recommendations. I’m not sure we would see a large missile like that or that large of an event, but we might. In any case, a 20-inch transparency is unwieldy for most detailed topographic maps. If you have a 1:60,000 or 1:250,000 scale map, however, you can scale accordingly and thus be extra safe. In any case, after this article you will have the skill to draw the transparency plume with whatever degree of safety you feel is adequate. Use the map scale and the CDC website to help you decide how large to create the rectangle.

So you now have the maps with your routes, alternate routes, and CBRN-relevant features identified, and you just received the location of a CBRN incident. Luckily, you caught the prevailing wind direction in the report. You take out your plume transparency and lay the dot on the transparency over the place where the event occurred. While holding the dot in place, perhaps with a thumb tack or push pin, rotate the plume transparency until the middle line of the transparency matches the direction of the wind with most of the transparency pointing downwind. Trace the transparency. Maybe your map is laminated and you can do this with dry erase marker or maybe you can use a pencil. Now, you have a map of your AO, with key terrain and routes marked, with a rectangle somewhere in it. This rectangle represents contamination. You cannot travel into or out of this rectangle. If you are in it, you need to begin protective measures immediately. I will not discuss protective measures here. There are ample articles in the Survival Blog Archives to help you. If you are not in the rectangle (the contaminated area), but the rectangle is between where you are and where you want to go, you will have to find new routes to where you want to go.

Winds change. The easiest way to track wind changes outside of the weather channel or a hand-held device is to use a weather vane. I found you can make a simple one using a straw, card stock, a pushpin, and a pencil. You can also use some leaves, grass, lint, or smoke along with a compass. Throw the leaves, grass, or lint in the air, and see which way they fall, and shoot an azimuth with your compass. Hunters use a scentless “smoke bottle”. To make a smoke bottle, put some talcum powder in a small Visine or contact solution bottle. Simply squeeze the bottle, look at where the mini-plume of talc goes, and shoot an azimuth with your compass. Hunters use this little trick, and if you do not want to make one, you can purchase one at any store that has hunting equipment. Keep this bottle or weather vane with you, and you will be able to track wind direction. As winds change, rotate the plume transparency middle line with the direction of the wind change, and trace again. Repeat as the wind changes. Every time a major wind change occurs, you should retrace the plume transparency because as winds change, the contaminated area grows further limiting your mobility. Yes, your areas will overlap, but that is okay; everything within the rectangles are contaminated. Within a four hour time frame, prevailing winds probably will not change, if it is in the middle of the day or night, but during transition times, such as dawn or dusk, day to night, or night to day, winds can and do change so you might have to continue tracing.

Also remember the peripheral effects of that new contaminated area. There will be lots of official activity within that plume area, and if you are in that area uninvited, you just might be forcibly cleaned. The Czech Republic decontamination unit, which conducted the cleanings for OIF, described something that was not my idea of a fun evening on the town. More than 20 soldiers tearing all the clothes from your body, hosing you down with high pressure water hoses, strapping you onto a clean steel table, and then scrubbing every inch of your body with long handled bristle brushes is not pleasant. It often resulted in broken skin, which my Czech comrades said was not that big of a deal. I guess I am saying it is probably in your best interest to avoid the plume at all costs, unless you have an affinity to 20 plus people, armed with two-foot long brushes, bearing witness to your birthday suit.

The purpose of the IPB, as I outlined it, and the plume transparency is to provide you with advanced situational awareness. This advanced situational awareness will help you decide to stay in or bug out because you will know how much of the terrain is denied to you in terms of mobility. You will be able to know whether or not you can execute your primary route or secondary route, or need to find a tertiary route in the moment, while at the same time responders are just beginning to lock down the area. If the plume is close enough or even in your immediate location, you can take preventative measures to reduce exposure probably before the contamination reaches you, all while avoiding unnecessary contact with responders. The sooner you make your decision, the greater mobility you will have.

If your decision must be delayed by a few hours due to unforeseen circumstances, some knowledge about weather and terrain may be helpful in determining plume propagation beyond the initial few hours. As time elapses, confidence in your traced rectangle degrades because the plume is subject to more variables. Wind speed and temperature affect plume propagation as does terrain. The net result of these variables is reduced confidence in your traced triangle. In other words, certain weather conditions may force you to adjust the contamination area.

Examining the various variables associated with plume propagation is extremely difficult and fraught with inaccuracies. What I am suggesting here is simplified to help you evaluate the situation quickly. There is a balance among air temperature, soil temperature, precipitation, wind speed, wind direction time of day, presence of an inversion, type of agent, how much of the agent, etc. that is too hard to describe in an article let alone a large simulation model. There are some generalities, however, that will assist in your decisions based on a few parameters: wind speed, temperature, terrain, and inversion presence. I will address each of these in terms of confidence in your plume rectangle.

Intelligence Preparation of the Battle of Your Area of Operation

I am sure it goes without saying, but have several maps of your AO. I get my maps from USGS for free, download them to a computer, and manipulate the images digitally so I can customize what I need. You can also pay USGS the $8 or $9 per map, but the digital maps are free when downloaded. I usually use the 1:24,000 scale maps, and that is what I will use in this article. The better quality of the map, the better decisions you will make, but any map is better than no map. Just keep in mind you will need to work within the scale of the map.

Within your AO, make sure areas of water–ponds, rivers, lakes, and streams are well marked. Are they accessible by improved roads? If so, and your commuter route or bug out route crosses these water features that are accessible by large vehicles, then make sure you have an alternate route. This same idea applies to local schools, stadiums, hospitals, and any area with a lot of infrastructure, rooms, phones, and antennas, as well as large open areas, like parking lots or fields. These will become CPs for responders. All improved roads (hardball roads that have blacktop or concrete as a surface) into and out of this area will only be accessible for official vehicles. I say improved because mobile decontamination vehicles, like the M93 Fox (used by the U.S. military) are well over 17 tons (maybe as much as 20 tons when combat loaded). Responders may not risk using roads that cannot support this large of a vehicle.

Now mark your primary and alternate routes to and from work and to and from your bug out location. Ask yourself, “Are these routes near any of the above objects? Near a water source? Hospitals? Stadiums? Large open areas?” If so, consider adding a tertiary route. In the army, we used the acronym PACE: Primary, Alternate, Contingency, Emergency when constructing plans or signals. Now your map may get too cluttered highlighting four different routes for your commute and bug out location, so you do not have to address PACE, just have a good working knowledge of your AO. Odds are you will have some time to lay out your plume IPB and find a new route.

Wind Speed

FM 3-6 has four different categories of wind speeds. We can probably get away with one delineator–winds at 13 mph. According to the Beaufort Scale, winds greater than 13 mph mean that, “Small branches move, flags flap, waves have some whitecaps”. If this is occurring, then your plume rectangle might only be good for two hours, expanding beyond the three miles longitudinally, with some minor reduction in the 1.5 mile width. In other words, you would need to expand your rectangle from eight inches to maybe ten inches, but reduce the width of the rectangle by an inch. Use caution if you are going to change the dimensions of the triangle; remember, these are guidelines, not fact. Persistence of the agent generally degrades with higher winds. “Persistence” means how long the agent will remain, if no decontamination occurs. If the amount of agent dictates that it will persists for say three days, and winds stay above 13 mph, then agent persistence might reduce by 12-36 hours.

If winds are below 13 mph, assume your rectangle is good, and stay away from that area as well as the fringe areas. As time elapses, be prepared to expand your rectangle by an inch in all directions every four hours or so.


Generally speaking, the higher the temperature, the less persistent the agent and more readily the plume will spread. There is a greater risk to individuals, however, as temperature increases. Perspiration on your skin will be more apt to absorb some agents. FM 3-6 draws your attention to this fact, so stay covered up, even if it is 100 degrees outside! So, the hotter it is, the more likely the actual plume will match your plume rectangle plus an increased chance that the plume will exceed the 1.5 mile width and 3 mile length as time elapses. By the end of four hours, with high temperatures such as in the summer, areas outside your rectangle may be contaminated. High temperatures also reduce agent persistence, but this depends very strongly on the type of agent, as some agents will increase persistence with an increase in temperature. Cold temperatures, as in winter, however, will increase agent persistent 12-48 hours, depending on the agent.


Complex terrain, such as an urban environment make tracking the plume that much more, well, complicated. One way to compensate for the complexity of urban terrain is to draw an 8 x 8 inch square, instead of rectangle, which I would recommend doing if any part of your AO is considered urban or even suburban terrain. Concrete buildings, cars, pollution, and so forth all dramatically alter both wind speed and temperature’s effect on plume propagation. The only way I would trust my plume rectangle is if winds were closer to 20 mph. If terrain is flat, or low rolling hills, trust your plume rectangle. If terrain is heavily wooded, the overall plume rectangle will be smaller, so trust it, and if you had to, you can maneuver closer to the contaminated area. Any terrain features alter plume propagation making any estimate fundamentally unreliable. The way we correct for it is to make our rectangle a bit more square or simply make the rectangle larger in both length and width.

Inversion Presence

An inversion is when hotter air lies on top of colder air. On the eve of our invasion of Iraq during OIF, there was an inversion at 2000 feet, which is perfect for deploying chemical weapons. An inversion means that no agent is lost to the upper atmosphere through diffusion; all agents are pushed back down to Earth’s surface, due to this pressure difference caused by the hot air on top rather than closer to Earth. This means that you may have to track the plume longer than the three days usually associated with a large Sarin release. It could mean that contamination could continue to spread in the plume beyond five days, so you will have to continue to track the plume beyond what is initially thought. The weather channel and local news generally does not report on this inversion. Luckily, the tell-tale signs of an inversion are not overly complicated. You can spot an inversion when “mist, fog, or dew is visible, smoke or dust hangs in the air and moves sideways, just above the surface; and cumulus clouds that have built up during the day collapse towards evening,” (Grains Research and Development Corporation, November, 2011). Again, presence of an inversion means that responders will be doing their job longer, and the plume will propagate further than anticipated based on the kind of agent used.

Summarized Steps

There is a lot to digest in this article from plume definition to identifying a potential inversion. Below, I will wrap up all that I have discussed in simple steps. If worse comes to worst, you could print this article, cut just this part out, and put it in with your maps.

Before a Chemical, Biological, Radiological, or Nuclear Incident:

  1. Highlight or make note of any key terrain associated with the plume: sources of water (rivers, lakes, ponds, streams), open fields, stadiums, schools, and hospitals.
  2. Highlight commuting route (primary and alternate). Routes from commute to bug out location, (primary and alternate). Routes from home to bug out location.
  3. Create plume transparency. This assumes a 1:24,000 scale map. Cut out an 8 x 4 inch clear transparency. Outline the rectangle. Bisect the rectangle with a drawn line down the middle of the long edge. Mark a dot where this bisector line intersects with one of the short edges. Keep with your maps along with a thumb tack or push pin.

After CBRN Incident Occurs:

  1. Remember, you are making the decision, “Do I bug in or bug out?”
  2. Take plume transparency, put dot on transparency over where the incident occurred. Stick push pin in dot.
  3. Rotate transparency so that the bisector line aligns with wind direction. Trace rectangle so that what you are tracing is on the map, not on the transparency.
  4. Check weather conditions. If the wind is not moving tree branches or flags, trust your rectangle. If tree branches and flags are waving, your rectangle may only be good for two hours, and you will have to retrace.
  5. Make a decision by answering these questions: “Am I in the rectangle?” Yes, then stay put and begin preventative measures.

If no, then look at your routes. Do any of your routes go through the rectangle? Are there any key terrain features near the rectangle that may interfere with your routes? If yes, use an alternate route or draw a new route. If no, then assess if you will have to move after four hours–are you in the downwind area? Are you currently located in line with the rectangle bisector line, but just outside it? Then, after four hours, you will be in the plume and need to move.

Will your bug out location be in the plume? If yes, then bug in. If no, (and you can move), move to your bug out location (or whatever your preference is).

Please remember, this is a situational awareness aid to help you decide whether to bug in or bug out. If you have a computer, by all means run the ALOHA program and get better estimates. If you still have questions, I encourage you to read FM 3-6; it is really informative. Plus, if you plan on defending your home, this FM is great for instructing you on how to use smoke screens effectively!

I have shared with you a methodology we used during OIF to help keep the troops and people of Kuwait safe. Hopefully this article will enable you to make an informed decision about whether you should bug in or bug out in case that brown smoke, such as in the Boston Marathon Bombing, is something other than just brown smoke.

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