Jun '25 • General Discussions
Safety
Let's talk a little about safety. Some of the things that members may post here may have a bit of danger associated with them. Those of us who have been in the amateur, and professional, scientific community for a while usually know how to assess the safety related aspects of an experiment. Sometimes, this is via the School of Hard Knocks, where we've survived close encounters with injuries. Mostly, however, it's due to being able to consider all of the possible ways that an experiment can go wrong, and taking steps to protect oneself from that. But, for many beginners, they don't have the experience nor wisdom as to how things may go wrong.
Thus, I think it's appropriate to include safety warnings for all potentially dangerous experiments, even if this gets to be a bit boring for the more experienced experimenters. However, even with warnings, everyone should understand that it's impossible to cover all of the possible ways something can go wrong, so some responsibility needs to be assumed by the experimenter. And, while many of the precautions may seem extreme, sometimes those precautions may save one from serious injury. Also, remember that, just because something worked once, doesn't mean that it will work every time. And, familiarity breeds contempt.
Many of my experiments have involved electricity (given that my training is as an electrical engineer). A common danger associated with that is high voltage electrical shocks. A few of the safety precautions are to always keep one hand in your pocket, while working with high voltage, such that any accidental contact won't cause current to flow through the chest area, and cause cardiac arrest. Standing on an insulated floor is also a good idea. Having an emergency power off (EPO) switch, which can be activated easily, is another good idea (Remember that an electrical shock may paralyze muscles, such that you can't "Let go", so an EPO button that you can "hip check" may be desirable.). Another precaution is to include bleeder resistors on high voltage power supplies, and then realize that these bleeder resistors may fail open, such that they don't remove the high voltage. Therefore, it's good to include redundancies (paralleled resistors), as well as using a "hot-stick" to discharge any capacitors which may retain a charge. Also, realize that some capacitors have the annoying tendency to build up a charge, even once they're discharged, and to hold that charge for a seemingly impossibly long period of time (I've seen the aquadaq coating capacitor on a CRT store a 27KV charge for over a week!). Also remember that even a mild electrical shock can cause uncontrolled muscle movement, which may propel your arm in a sharp object, and produce a nasty and painful cut.
Some high voltage circuits can produce appreciable x-ray radiation. It's not good to play with things which make you glow in the dark. Use appropriate shielding, for yourself, and any innocent bystanders (who may be standing on the other side of a wall).
Another danger is high currents. Even if only a few volts are involved, it's still possible to have currents well into the hundreds of Amperes, if not more, and currents of this magnitude will cause extreme heating, which can cause metal components to melt, vaporize, explode/sputter, or start fires (as well as branding a careless experimenter who comes into contact with it). While it's generally recognized as desirable to leave your mark on the world, that doesn't extend to leaving a bit of your charred skin on an overheated component.
Yet another failure mode is for components to undergo a rapid unplanned disassembly (e.g., They explode!). Eye protection is a good idea, since even a tiny shard projected into one's eye can cause permanent blindness (which really sucks!).
Some devices can fail by letting the magic smoke out (Consider the case of applying too much voltage to an electrolytic capacitor, which tends to produce an ear-shattering KaBOOM, accompanied by a large cloud of Borax steam.). Unfortunately, this magic smoke can sometimes be quite caustic and irritating. Don't breathe the magic smoke, and have a way of ventilating the experimental area should this occur.
It's not a bad idea to be accompanied in the lab by someone who knows how to activate the EPO button, should something bad happen. It's also a good idea if they know how to perform CPR, should the experimenter be shocked into cardiac arrest. And, having a fire extinguisher, rated for electrical fires (and knowing how to use it effectively) is usually a good idea, too.
Some opto-electronic experiments, such as with lasers, flash tubes, and even ultra-bright LEDs, may produce intense bursts of light. Be especially wary of ultraviolet and infrared light sources (since Photokeratitis is really painful!). One of the primary rules for laser users/developers is, "Don't stare into the laser with your remaining good eye.". As someone who has undergone laser eye surgery, I can tell you that laser radiation into an eye HURTS LIKE HELL! Even a ultra-short burst, for example, 25 milliseconds in duration, will sear the retina of an eye, and produce a permanent blind spot (Blink response time is on the order of 330 milliseconds, so the damage occurs over an order of magnitude faster than you can blink!). Plus, laser radiation has an notorious habit of finding specular reflection surfaces, and bouncing in crazy directions. Wear appropriate eye protection, which may involve laser goggles, which filter out the laser frequency in use, while still allowing you to see.
Many chemical processes used in the field of electronics have their own risks. I have a great Tin plating solution recipe. Unfortunately, it's based on Sodium Cyanide. A splash of acid into that bath will release Hydrogen Cyanide gas, and one whiff of that, and you'll be dead before you can even hit the floor! There are many great Silver plating recipes out there, which are frequently used, since Silver makes a great electrical conductor. Unfortunately, some of those are based on Cyanide, and some of the others form explosive compounds upon sitting. Quartz crystal processing uses HydroFluoric Acid. A tiny splash of that on your exposed skin will produce an extremely painful sore, which takes forever to heal, as well as dissolving the Calcium from bones, and can cause immediate heart failure, by upsetting the Sodium/Potassium/Calcium balance in the blood stream (Keep a supply of Calcium Gluconate as an antidote, in case of accidental exposure.). Ferric Chloride, a typical etchant for printed circuit boards, is mostly benign, except it will produce permanent yellow-brown stains on anything it's splashed on, it will eat holes in clothing, and it hurts like hell if you splash it into your eye. The resulting Copper Chloride spent solution is fairly toxic to plants, so have a good way of safely disposing of it (Of course, that should apply to all chemicals; Have a plan of how to safely dispose of them. And, flushing them down the drain is usually not a good idea.).
I'm sure I've missed some rules, but the general idea is to think of all the ways that something can go wrong, and make plans to handle those situations. Remember that Murphy was an optimist, and things will often go so very wrong, even more so than Murphy's Law predicts.
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Safety
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