The Risks of NPE “Non-Detectible” Knives

Recently, Morgan Atwood, founder of BFE Labs, wrote a post for his website entitled, “Failure of Carbon Fiber Knives to Pass Metal Detector Screening,” in which he announced a wholesale policy change in the site’s sales of carbon-fiber blades for “NPE,” or Non-Permissive Environments. This refers to the practice of weapons that aren’t detected, or detectible by, metal detectors. If you carry a plastic “CIA Letter Opener” into a baseball stadium where the property owners have metal detectors, you are entering an NPE.

Morgan’s article reads, in part:

Over the past 18 years as a knifemaker, non-metallic knives have been a primary specialty of my shop. Like many other makers, Carbon Fiber has been the material of choice for the majority of those blades. Carbon Fiber (CF) has proven qualities of strength, toughness, and cutting ability that exceed other non-metallic composites.

Many other knifemakers have used CF in building tools for non-permissive-environments (NPE)… I have recently discovered that we were all wrong. Carbon fiber knives CAN be discovered by a metal detector.

Morgan links to a video called, “EM Field Eddy Current Induction in Carbon Fiber And The Implications For NPE Tools.” In the video, he and his business partner discuss their findings and demonstrate that a metal detector can indeed detect carbon fiber knives. His article goes on,

Perhaps needless to say, I will no longer be producing carbon fiber knives. Between myself and the other makers working in this field, a reasonable estimate is that there are thousands of carbon fiber knives in existence, and being relied upon. That practice is no longer recommended, as clear evidence shows they are not suitable for NPE use.

The explanation for why carbon fiber knives can be detected — and why more people weren’t aware of this before — is a little technical, but seems to revolve around the fact that a metal detector generates a magnetic field that generates electric current inside the metal object detected. This current is received by a coil in the detector and, while carbon fiber is non-metallic, it is a conductor. This will create a return magnetic field, although the angle at which the CF knife is held relative to the detector makes a difference. Sloppy technique used when people are “wanded” may account for CF knives slipping past security at some checkpoints, and it may also be the case that carbon fiber doesn’t generate as MUCH current as a metal knife does.

Interestingly, BFE Labs did not merely switch production of carbon fiber knives to G10, a fiberglass laminate that does not trigger metal detectors. The company further announced, through Morgan, that anyone who bought a BFE Labs carbon fiber knife is owed a replacement G10 knife, or a discount on a future purchase if they choose not to have the carbon fiber piece replaced. That seems to me like going above and beyond the call of duty in service to your customers. Most companies would simply issue a warning about the carbon fiber being detectible and leave it at that.

Your Options for NPE Carry

Setting aside all that for a minute, what are your options when it comes to non-detectible, non-metallic knives? We should first admit that no knife is non-detectible. There will always be a way to detect it, even if it is through a good, old-fashioned pat-down search. And there are knives that have gotten through checkpoints that had no business doing so because the people operating the checkpoint were just people. People can be sloppy and inattentive, but you don’t want to base your whole plan on the hope that whomever checks you over will be phoning it in that day.

You can buy a ceramic knife, but these must be checked meticulously to make sure they don’t contain hidden metal. Ceramic blades are very hard, making them relatively brittle and virtually impossible for you to resharpen. They won’t need much in the way of sharpening, though, especially if you resist the urge to use your fancy ceramic self-defense tool as a day to day utility knife. Honestly, you should be carrying a regular utility knife anyway, but of course these might not make it past a checkpoint depending on the type of security that is in place.

As is now obvious, carbon fiber was once thought to be an option, but no longer is. G10 is a pretty good material, although don’t try to make one yourself. G10 is absolutely evil stuff to work and you must never breathe the dust from grinding it. Let someone else who knows how to handle it make the G10 knife for you, and then carry that. It won’t be very sharp compared to a ceramic blade or a steel knife, so these don’t make the best cutters. They’re better used for expedient stabbing.

You could even go old-school and choose wood. Wooden blades do have a history, as do fire-hardened sticks used for poking. I don’t know if you’re planning on staking any vampires, but they’re reasonably good for that, too. I’ve seen some wooden “trainers” that could poke pretty hard, and there are even purpose-built wood tools made for self-defense (like yawara sticks).

Finally, you could go with plastic. This is your basic glass-filled Nylon or even straight plastic CIA “letter opener” type tool. They can be sharpened with a pocket knife but don’t rally hold an “edge.” They might slice you a little bit, but they’re not really useful for cutting, as they’re still just plastic. They are, however, expedient stabbing weapons as long as you stick to softer targets like the eyes, the hollow of the throat, or the face in general. Plastic knives like this are among the cheapest of the NPE tools on the market. Some do have hidden metal inserts, though.

The Dangerous Game of NPE Carry

This does raise an interesting issue, too, and that is the issue of the dangerous game some of us are playing with non-detectible — or supposedly non-detectible — knives. First of all, obviously, if you have a knife that you think has no metal in it, you need to think again. A lot of manufacturers actually insert metal into, say, knives with ceramic blades, specifically to prevent those knives from being passed through security checkpoints. As those who bought carbon fiber knives might have learned to their detriment, even things you think aren’t going to trigger the detector might.

More abstractly, though, stop and ask yourself why you are buying knives for NPE use in the first place. We at The Martialist are staunch defenders of your right to defend yourself, but we don’t want you to go to jail, either. You absolutely must weigh the risks when it comes to carrying any sort of weapon in an area you are not supposed to have it. Never, ever try to get an NPE blade past a checkpoint run by the government, for example, such as your local federal building or at an airport. These are serious crimes and you won’t like the results if you get caught.

But, you might be thinking, “What if I’m carrying an NPE knife in a location that, if I’m caught, merely results in me being thrown out?” Well, that’s your call. Everybody’s standards are different… but understand that even if you think the consequences aren’t serious, you could be charged with trespassing if the private location is serious about protecting its premises from you being armed.

Another thing to consider is that not every security checkpoint involves a metal detector. Those machines they use at airports can detect any hard object under your clothes, no matter what it is made out of (which is how it sees you naked). No knife, no matter what the material, will clear a checkpoint like that, and if you risked that you’d deserve to get in serious legal trouble for it (because it would be stupid to try).

If you’re determined to take a plastic knife past a checkpoint where there is no legal penalty for so doing, though, there’s only one way to be sure. Metal detectors aren’t cheap, but you can find some handheld metal detector wands that work okay and that are reasonably affordable. I bought one specifically to test supposedly non-metallic knives. Even that is not a 100 percent verification because the “real” detectors you face will be more expensive and more accurate… so long as the people wanding you use proper technique.

As with anything in life, there’s always an element of risk. Be careful out there. Getting charged with a crime can put a serious crimp in the rest of your life. Remember, we, as martialists, are the good guys. We should be conducting ourselves in accordance with the law and, when the law is stupid, the way to fight bad law is to fight to change it. As bad as it is out there, we have indeed seen positive changes at the state level. Work for this. In the meantime, be more clever than the opponents you’ll face.