CBRN, previously called NBC, stands for Chemical Biological Radiological and Nuclear. In short, it encompasses the variety of threats that require a gas mask. A CBRN event alone constitutes a serious SHTF scenario in anyone's book, and in an otherwise unrelated SHTF scenario there is a high possibility of a CBRN event taking place and making a bad situation worse. Only a few years ago a fire in Santa Clarita, Ca (less than 60 miles from me) set a large amount of chlorine on fire, releasing it into the air as a gas threatening first responders. CS Agent (tear gas) also falls under the CBRN spectrum and is defended against using similar equipment. Trucking accidents are fairly common and many involve hazardous chemicals. I just want to give a rundown of CBRN defense and some recommendations, do note I do not claim to be a professional expert and this is solely my own understanding of the subject based on what I have learned from actual experts. I will post reference material at the end of this writeup. Definitions of CBRN: Information from Guidebook for Marines 21st- edition I. Chemical Chemical threats are toxic agents used for a variety of purposes. Weaponized chemicals include gases such as chlorine and VX Agent (nerve gas) and are outlawed under numerous treaties including the Geneva Convention, however they are not difficult to synthesize. Industrial chemicals can pose significant risk in the event of an accident or spill, which is far more likely than an actual attack. Many are highly reactive and can form explosive compounds with gases already present in the air. Since many take the form of a gas most chemicals will require at least a respirator to protect against, many more dangerous agents (nerve agents, blister agents) will harm on contact and require a full suit. Some gases, such as chlorine, displace oxygen and require a self-contained breathing unit. II. Biological Biological threats consist of disease-causing pathogens. Weaponized diseases are also outlawed by numerous treaties and are very difficult to create. Again, any significant outbreak in the US is likely to be accidental (or "accidental") and non-military. A respirator provides more than enough defense against most pathogens, however a full suit is recommended for close contact with patients or disease-bearing fluids. Recommended protection can vary depending on the method by which a threat is transmitted. III. Radiological Radiological threats are radiation or radioactive materials, typically in the form of fallout. A good example is a dirty bomb, a nuclear device which produces a small, localized detonation but produces large amounts of radioactive fallout. A full suit is recommended for long-term exposure however simply avoiding exposed skin goes a long way. Inhalation is the biggest threat- a respirator is most important. Avoiding exposure is key, remain under cover if at all possible. Radiological threats are typically very rare, a nuclear airburst (most bombs) will produce little fallout and there are only two reactor meltdowns on record. Natural disasters such as earthquakes can cause complications however, as seen at Fukushima, Japan in 2015. IV. Nuclear Nuclear threats are posed by actual nuclear detonations. Nuclear defense consists of surviving the initial blast and the accompanying radiation, most of which is thermal. Again, avoiding exposure is key. The initial blast will produce a large shockwave and massive amounts of thermal radiation. Thermal radiation will burn exposed skin (the kind where your flesh peels off in chunks) but is a line of sight effect. Seek protection in a trench or foxhole away from potential debris to protect from both the shockwave and heat. The single best practice to survive a CBRN incident: Leave the area. Protective equipment will help you survive an event, however it should be used only as a means of escape. This isn't S.T.A.L.K.E.R, we have no business intentionally entering a contaminated area for any reason.