You’ve probably heard that a F/A-18D jet crashed in San Diego on approach to Miramar, killing 3 on the ground (the pilot ejected and is fine). A lot of the news reports noted that ~20 homes were evacuated due to ‘toxic chemicals’. What sort of chemicals would you be worried about?
First Responders and Bystanders
Beyond the physical hazards (things under pressure like hydraulics, O2 canisters,…etc), there’s all kinds of stuff to worry about like fuel, oils, hydraulic fluids, beryllium, lithium, chromium, mercury, and possibly radioactive compounds. But the biggest hazard is simply the burning of Advanced Composite Materials (ACM). According to the military, aircraft can contain anywhere from about 175-33,000 lbs of ACM. Upon burning, a lot of these Advanced Composite Materials release lots of carbon monoxide (obviously), nitrous oxides, sulfur dioxide, and hydrogen cyanide. An air craft explosion could produce these chemicals above levels that would kill you in short order as long as the temp was above 300 deg F. The F-18 has a lot of Graphite-epoxy ACM which is probably better short term than if an Apache helicopter crashed due to the kevlar/graphite-epoxy used on that aircraft. So, in short, you’re most worried about death from CO or cyanide poisoning. After that you’d worry about the more exotic stuff, but it’s not likely that you’d be exposed to this junk after the crash so it’s not as big of a concern.
The Clean-up crew would have to think about all the exotic chemicals abounding but would not have to worry so much about the CO/NO/SO/CN issues. They would, however, have to worry about all the respirable fibers that may be floating around due to the ACM. Particularly troubling are the boron-epoxies since they are able to penetrate protection to some degree. These fibers cause long-lasting harm if inhaled in sufficient amounts.
Bonus explainer: How do you respond to an aviation crash?
If we’re talking about you the citizen, the answer is to stay inside, close all windows, doors or other air intakes and wait for instruction. If you’re talking about the responders, they evacuate the area around the crash and smoke plume, and cool the crash site down while trying not to break apart the plane further with high pressure. They do not use aircraft (such as helicopters) around a crash because it disperses the chemicals downward and in an unpredictable manner. Once they’ve identified the immediate hazards (always using proper industrial hygiene, of course), they spray a fixicant like acrylic floor wax over the crash to keep fibers and chemicals where they are.