Homemade Chemical Bombs

This is a little bit out of the terrorism realm, but there is an interesting article about ‘homemade chemical bombs’ in the most recent CDC Morbidity and Mortality Weekly Report. These really are not improvised explosive devices, they don’t have that kind of power, but they do cause casualties in middle-America on a fairly routine basis.

Generally speaking these ‘devices’ are not truly explosives because fire is not involved. Some sort of simple chemical reaction (or phase change) causes the production of a gas. The amount of gas produced in a closed container many cause a catastrophic failure of the container, accompanied by a loud bang (or soft boom) and frequently a visible gas cloud. That gas cloud is usually responsible for the more serious injuries associated with these devices because of the toxicity of the gas.

There is little authorities can do to prevent teenagers (chronological or developmental) from constructing these devices. The components are readily available in the home or hardware store. The more effective of these devices (measured by the sound of the boom or size of the gas cloud) do require slightly more expensive chemicals, but these can usually be obtained from high school or college chemical store rooms.

Frequently these ‘bombs’ are made in plastic soda bottles so they have a relative low probability of causing blast or shrapnel type injuries. When made in glass containers or PVC pipe there is a low-level shrapnel (Purists please don’t’ complain that ‘Shrapnel’ comes from a specific type of Civil War era munition, common usage includes flying pieces of bomb casings of any type) hazard, but only very close to the detonating device.

Having played with these things in my youth (long before the Internet we had Headly’s Formulary or the Anarchist’s Cookbook) I can testify that most of the people injured by these devices are the ‘bombers’. These devices typically don’t include fuses; they rely on the speed of chemical reactions and the quality of the ‘bomb case’ to determine when they will actually ‘detonate’; too many variables for the limited attention span of teenagers to perfect.

They are potentially dangerous, the danger increasing as you get closer to the device. The biggest danger to first responders is not being able to tell in advance what the resulting chemical cloud will be. The CO2 cloud from a ‘dry-ice’ bomb is relatively non-hazardous; the chlorine gas from a bleach-bomb can be toxic to severely irritating depending on the amount produced and local ventilation conditions.

There is one type of these chemical bombs that is slightly more dangerous and that is because it produces a very flammable hydrogen gas-cloud. The initial detonation of these ‘aluminum’ bombs is the typical gas pressure reaction, but the resulting gas cloud (depending on local conditions) can result in a secondary explosion producing fire and flying debris.  

All first responders and emergency medical personnel should read the CDC article.

‘Chemical Bomb’ Thrown at Protestors

A short article on WGME.com has created a minor stir on the Internet including calls for a Homeland Security response. The reason for this is that the article describes an incident at the Occupy Maine encampment in Portland, ME; the incident involved a ‘chemical bomb’ thrown at into the tent area. The problem is that the term ‘chemical bomb’ conjures up images of sarin causing multiple, hideous deaths. The device used in Portland had nothing to do with chemical weapons.

The Devices

What the article actually describes is a fairly common device used to ‘attack’ mail boxes across the country; “a bomb made of kitchen chemicals in a Gatorade bottle”.  There are a number of variations of this ‘explosive’ device depending on the particular combination of chemicals used. They all consist of two or more chemicals sealed in a plastic container. The two chemicals react producing some sort of gas. As the gas production proceeds pressure inside of the bottle increases until the plastic container can no longer contain the pressure. The container ‘catastrophically’ fails producing a large pop and spraying the residual chemicals over a relatively small area.

Chemical Risk

Depending on the chemicals used, there may be a minor residual chemical threat involved. If cleaning chemicals (containing ammonia and bleach) are mixed the gas given off is chlorine gas. The amount of this toxic inhalation hazard (TIH) gas produced is seldom more than irritating unless it is detonated in a small enclosed area. A drain cleaner bomb produces hydrogen gas which is flammable, but the main risk is being sprayed by the caustic drain cleaner. Other chemicals produce different hazards.

I want to be careful not to overly minimize the potential chemical hazards associated with these devices, but they are not typically life threatening. Actually, the case can be made that the person assembling the device is at more of a danger of chemical exposure than people in the general area where the device goes off. Of course, no one should handle these devices if they are found without extensive protective clothing and specialized training.

Chemical Explosives

There is a significant portion of the population that over reacts whenever the word ‘chemical’ is used to describe something. Their visceral reaction is due, in large part, to a comprehensive misunderstanding of chemistry; they equate ‘chemistry’ with all sorts of horrors perpetrated upon humanity by multi-national chemical companies.

Take for example the term ‘chemical explosives’; all explosives are chemical explosives (okay an argument could be made for excluding nuclear bombs). They either require a chemical reaction to produce gasses that that in turn produce pressure or they undergo a phase change (from solid or liquid to gas) that results in the increase in pressure. In many cases the reactions are fast oxidation reactions that we generically call fire.

The True Import of this Chemical Bomb Attack

The explosives used in this case do not produce a great deal of energy and any damage is very localized, barely being enough to damage a mail box. In fact, most law enforcement personnel encounter these devices in mailboxes; a common suburban/rural student prank.

While this particular attack was made upon a ‘political’ target, it is very likely that this was a juvenile prank rather than a political attack on the protestors. If it was a political attack, or even a politically motivated prank, it substantially backfired (as such attacks usually do) in that it provided the protestors with some sympathetic press coverage.