WEBVTT - Rerun: How Smoke Detectors Work 0:00:04.320 --> 0:00:10.640 Welcome to Tech Stuff, a production of Iheartradios How Stuff Works. 0:00:12.240 --> 0:00:14.800 Hey there, and welcome to tech Stuff. I'm your host, 0:00:14.920 --> 0:00:18.560 Jonathan Strickland. I'm an executive producer with iHeart Podcasts and 0:00:18.720 --> 0:00:22.599 how the Tech are you. Well, I'm still vacating, which 0:00:22.640 --> 0:00:27.440 means I'm off in Florida being a crazy tourist type person. 0:00:28.000 --> 0:00:31.080 And in the meantime, I have an episode for you 0:00:31.320 --> 0:00:34.519 that we publish back on February tenth, twenty twenty. This 0:00:34.520 --> 0:00:37.080 one is titled How Smoke Detectors Work. I figured it 0:00:37.120 --> 0:00:39.480 was a good idea to do an episode about smoke 0:00:39.520 --> 0:00:41.560 detectors as we go toward the end of the year, 0:00:41.600 --> 0:00:46.320 because I've always tried to change out the batteries and 0:00:46.400 --> 0:00:50.080 my smoke detectors at the beginning of each year, because 0:00:50.120 --> 0:00:52.080 otherwise I just would forget to do it. But by 0:00:52.120 --> 0:00:55.080 making it like, hey, happy New Year, you gotta change 0:00:55.120 --> 0:00:58.640 out all the smoke detector batteries, I am less likely 0:00:58.680 --> 0:01:01.280 to forget. But how did those darned things work in 0:01:01.320 --> 0:01:06.920 the first place. Well, let's listen and find out. Now. Clearly, 0:01:07.360 --> 0:01:11.759 smoke detectors are incredibly important because we all know fires 0:01:11.800 --> 0:01:15.000 can be life threatening. They can spread quickly, they can 0:01:15.040 --> 0:01:17.600 cut off potential escape routes for the people who are 0:01:17.680 --> 0:01:20.600 caught in the way. So early warning systems that can 0:01:20.640 --> 0:01:24.320 alert us to danger before it becomes a mortal danger 0:01:24.440 --> 0:01:28.400 are fantastic inventions. And there are a couple of inventions 0:01:28.440 --> 0:01:30.959 I want to talk about before we actually get to 0:01:31.040 --> 0:01:34.120 smoke detectors. I'm sure that doesn't come as a surprise 0:01:34.160 --> 0:01:36.320 to any of you who have listened to Tech Stuff 0:01:36.319 --> 0:01:39.319 episodes before. I always like to set the ground well. 0:01:39.440 --> 0:01:41.399 The first one that I want to talk about is 0:01:41.440 --> 0:01:45.600 the portable electric fire alarm, as in a fire alarm 0:01:45.640 --> 0:01:48.800 that works on electricity, not a fire alarm that detects 0:01:48.840 --> 0:01:53.040 electric fires. Francis robins Upton, who is a physicist who 0:01:53.120 --> 0:01:56.960 was a partner and general manager of the Edison Lamp Works, 0:01:57.440 --> 0:02:01.720 as in Thomas Edison, developed this particular invention back in 0:02:01.800 --> 0:02:06.080 eighteen ninety. Now, according to the patent, the design would 0:02:06.120 --> 0:02:10.280 sound an alarm after detecting that the temperature had risen 0:02:10.440 --> 0:02:14.520 above some predetermined limit, so if it got too hot, 0:02:15.120 --> 0:02:17.960 this thing would go off. And the way this would 0:02:18.040 --> 0:02:21.160 work was really clever. You can actually learn exactly how 0:02:21.160 --> 0:02:24.320 it was supposed to work based on the patent that 0:02:24.560 --> 0:02:29.640 Upton got on this particular invention. So the way it 0:02:29.680 --> 0:02:33.080 works is that there are a pair of electrical contacts 0:02:33.639 --> 0:02:36.160 and if they are in contact with each other, if 0:02:36.200 --> 0:02:39.720 they touch each other, it completes a circuit. But normally 0:02:40.120 --> 0:02:43.639 there's a gap between them and electricity can't pass between 0:02:43.760 --> 0:02:47.560 the two. It can't cross that gap, so it's normally 0:02:47.600 --> 0:02:51.280 in the off position. However, one of those two electrical 0:02:51.400 --> 0:02:56.080 contacts is mounted on a fixed arm and the other 0:02:56.400 --> 0:02:59.400 is on an arm that's attached to a coil of 0:02:59.480 --> 0:03:04.440 biomet hallick material. Now I mentioned biometallic strips in the 0:03:04.480 --> 0:03:07.400 episode about lighters, and it's something you find in a 0:03:07.440 --> 0:03:12.280 lot of different technologies that depend upon changes in temperature 0:03:12.720 --> 0:03:17.240 as a variable, like thermostats have bimetallic strips in them. 0:03:17.560 --> 0:03:20.040 And essentially what it is is a strip of metal 0:03:20.280 --> 0:03:24.120 that consists of two different metals. And think of it 0:03:24.160 --> 0:03:26.880 as like a metal sandwich, a top side and a 0:03:26.919 --> 0:03:30.480 bottom side, and one metal is the top side, the 0:03:30.520 --> 0:03:33.560 other metal is the bottom side, and each metal has 0:03:33.600 --> 0:03:37.040 slightly different properties, and one of those properties is how 0:03:37.120 --> 0:03:40.640 quickly they expand when they're heated up. You know, we 0:03:40.760 --> 0:03:43.560 know that metal expands as it gets warmer. Well, using 0:03:43.560 --> 0:03:46.640 a bimetallic strip, you have one side that will expand 0:03:46.720 --> 0:03:50.360 faster than the other side, and when that happens, it 0:03:50.440 --> 0:03:54.920 causes the strip to curl, so it deforms. As it 0:03:54.960 --> 0:03:58.839 gets warmer, one side is expanding faster than the other 0:03:59.360 --> 0:04:02.640 and you get this curled metal as a result. So 0:04:02.760 --> 0:04:07.240 with Upton's proposed invention in the patent, this coil of 0:04:07.320 --> 0:04:11.120 bimetallic material would act as sort of an actuator. As 0:04:11.200 --> 0:04:14.520 it would get warm, it would expand, and this in 0:04:14.560 --> 0:04:18.440 turn would create a pushing force on the arm with 0:04:18.640 --> 0:04:21.960 the electrical contact on it that then can move toward 0:04:22.160 --> 0:04:25.520 the other electrical contact that's in a fixed position. And 0:04:25.600 --> 0:04:29.680 so once the coil had expanded enough, the two contacts 0:04:29.760 --> 0:04:33.480 would touch one another and it would complete a circuit. 0:04:33.880 --> 0:04:37.479 At that point, electrical current could actually flow from a 0:04:37.520 --> 0:04:40.680 battery that was connected to this device all the way 0:04:40.720 --> 0:04:44.680 through to activate an alarm bell. So once the temperature 0:04:44.680 --> 0:04:48.120 got hot enough the two contacts touch, you get a circuit. 0:04:48.400 --> 0:04:50.800 The alarm bell goes off. If it cools down, the 0:04:50.839 --> 0:04:55.200 contacts will slowly separate, and eventually they'll separate enough where 0:04:55.240 --> 0:04:58.800 that electrical circuit can't be complete. Anymore, the alarm bell 0:04:58.839 --> 0:05:02.560 would go off. And Upton's invention was, without doubt a 0:05:02.680 --> 0:05:06.520 very clever one, and it could help save property by 0:05:06.560 --> 0:05:09.680 sounding an alarm before a fire had raged completely out 0:05:09.680 --> 0:05:14.680 of control. But there are many dangers with fires, and 0:05:14.800 --> 0:05:18.600 heat is just one of them. Another very serious danger 0:05:18.760 --> 0:05:22.320 is smoke, which not only obscures your vision, but it 0:05:22.360 --> 0:05:25.960 also can suffocate you as well. So while the alarm 0:05:26.080 --> 0:05:30.159 as design would work, it wouldn't necessarily be enough to 0:05:30.279 --> 0:05:34.679 save lives, or it might not save enough lives because 0:05:34.720 --> 0:05:36.960 it would only go into action after the temperature had 0:05:37.000 --> 0:05:40.960 already increased enough to make this bimetallic strip expand to 0:05:41.000 --> 0:05:44.760 a sufficient degree, and by that time it might already 0:05:44.760 --> 0:05:47.720 be too late for the people in that building. Now, 0:05:47.760 --> 0:05:51.320 as far as I know, Edison's company didn't actually produce 0:05:51.480 --> 0:05:54.040 any of these fire alarms, but they did patent it. 0:05:54.640 --> 0:05:57.320 Over in Great Britain, there was a fellow named George 0:05:57.360 --> 0:06:01.440 Andrew Darby who patented his own fire alarm, also triggered 0:06:01.520 --> 0:06:05.400 by an increase in temperature. But Darby's invention did not 0:06:05.680 --> 0:06:11.440 depend upon bimetallic strips. It depended on butter or some 0:06:11.560 --> 0:06:16.520 other material that melts at higher temperatures. Say what, all right, 0:06:16.640 --> 0:06:21.159 So imagine you've got a seesaw like contraption, a lever 0:06:21.320 --> 0:06:24.039 in other words, and the heavy end of the lever 0:06:25.160 --> 0:06:28.640 is up in the air actually because you have a 0:06:28.680 --> 0:06:31.360 weight on the opposite end of that lever. So it's 0:06:31.400 --> 0:06:33.599 like a kid sitting on a seesaw that doesn't have 0:06:33.680 --> 0:06:36.200 another kid at the end of it. The kid at 0:06:36.200 --> 0:06:38.600 the end of the sea saw weighs it down, and 0:06:38.640 --> 0:06:41.920 the free end of the seesaw is up in the air. Well, 0:06:41.920 --> 0:06:45.880 in this case, the fire alarms seesaw. The arm that's 0:06:45.960 --> 0:06:48.560 up in the air has an electrical contact point on it, 0:06:48.839 --> 0:06:52.120 and if the arm of the seesaw were to come down, 0:06:52.839 --> 0:06:58.479 that contact would complete a circuit, and thus electricity would 0:06:58.480 --> 0:07:00.919 be able to run from a battery through an alarm, 0:07:01.040 --> 0:07:05.480 very much like Upton's invention. So weighing down the other 0:07:05.600 --> 0:07:07.640 end of the arm. The thing that's actually keeping the 0:07:07.680 --> 0:07:10.960 electrical contact up in the air is a block of 0:07:11.040 --> 0:07:15.320 butter or fat or wax or some other material that 0:07:15.360 --> 0:07:19.160 can melt at higher temperatures. So as the temperature rises, 0:07:19.640 --> 0:07:22.800 the block begins to melt away, and eventually it melts 0:07:22.920 --> 0:07:26.040 enough so that the weight isn't sufficient to keep the 0:07:26.080 --> 0:07:28.160 other end of the seesaw up in the air, and 0:07:28.240 --> 0:07:31.400 it'll sink down and the contact will complete the circuit 0:07:31.640 --> 0:07:34.600 and the alarm will go off. I was amused to 0:07:34.800 --> 0:07:38.240 find a butter based fire alarm. I wasn't surprised that 0:07:38.280 --> 0:07:40.120 it came out of England, but I was amused to 0:07:40.160 --> 0:07:42.680 find it. I can think of a few potential problems 0:07:42.760 --> 0:07:46.480 with such an arrangement. For example, it might start attracting 0:07:46.560 --> 0:07:51.040 pests that could eat the weight, so in those cases 0:07:51.080 --> 0:07:53.480 you wouldn't actually have a fire alarm, but you might 0:07:53.520 --> 0:07:57.400 have a rat alarm, or it would just turn rancid 0:07:57.520 --> 0:08:02.480 and smell offul Still a pretty clever approach, but not 0:08:02.600 --> 0:08:04.880 one that I think you would actually want to put 0:08:04.960 --> 0:08:09.480 in your buildings. But these solutions weren't practical for homes 0:08:09.720 --> 0:08:12.160 or anything like that. As I mentioned, they wouldn't really 0:08:12.160 --> 0:08:14.400 alert you to the presence of smoke, which on its 0:08:14.400 --> 0:08:17.040 own would be enough to be deadly. So this was 0:08:17.080 --> 0:08:20.000 really looked at as more of a solution for things 0:08:20.080 --> 0:08:24.440 like factories facilities, where you've got a lot of industrial 0:08:24.520 --> 0:08:27.440 operations going on, where the risk of fire is high 0:08:27.880 --> 0:08:31.679 and the risk of property loss is also high smoke 0:08:31.760 --> 0:08:36.680 detectors also trace their history back to chemists, physicists, and inventors, 0:08:36.960 --> 0:08:39.439 and in fact, you could say that smoke detectors were 0:08:39.520 --> 0:08:44.680 made possible not just through exploratory science, but also happy accidents. 0:08:45.200 --> 0:08:48.520 And will begin with a super smart Swiss physicist in 0:08:48.600 --> 0:08:52.840 the early twentieth century and try saying that three times fast. 0:08:52.960 --> 0:09:00.640 Super smart Swiss physicist. His name was Heinrich Grinecker or 0:09:00.679 --> 0:09:04.400 Grindacre if you prefer study a lot of different stuff, 0:09:04.480 --> 0:09:09.160 including radioactivity. Wilhelm Runtgen had discovered the existence of X 0:09:09.280 --> 0:09:13.439 rays in eighteen ninety five, and Grindacre devoted a good 0:09:13.440 --> 0:09:17.000 deal of his work toward getting a better understanding of 0:09:17.640 --> 0:09:20.160 X rays and other forms of radiation, and to do 0:09:20.200 --> 0:09:23.920 that he had to overcome some practical obstacles. For example, 0:09:24.200 --> 0:09:26.800 he needed a device to help measure the intensity of 0:09:27.000 --> 0:09:30.040 X rays, and such a device didn't really exist yet, 0:09:30.120 --> 0:09:33.400 so he got to work inventing one. X rays are 0:09:33.440 --> 0:09:37.199 a type of ionizing radiation that means that when they 0:09:37.320 --> 0:09:42.120 encounter molecules or atoms, they can ionize them. And an 0:09:42.160 --> 0:09:45.040 ion is a molecule or an atom that has a 0:09:45.080 --> 0:09:49.599 net electrical charge, so it's either a positive particle or 0:09:49.679 --> 0:09:53.120 a negative particle. And a positive ion is one that 0:09:53.160 --> 0:09:56.560 has more protons than electrons, so you have a net 0:09:56.640 --> 0:09:59.080 positive charge. A negative ion would be the opposite, has 0:09:59.120 --> 0:10:03.120 more electrons than protons and has a net negative charge. Now, 0:10:03.160 --> 0:10:07.920 one thing Grindacre did was to create ions by building 0:10:07.960 --> 0:10:11.319 a grid of wires through which he could stream high 0:10:11.440 --> 0:10:16.199 voltage current. And you would pass air molecules essentially through 0:10:16.280 --> 0:10:21.679 this grid, and the current would strip electrons off of 0:10:21.760 --> 0:10:26.200 those particles, creating positive ions. So the grid was in 0:10:26.240 --> 0:10:29.520 this chamber through which gas could move, and as I said, 0:10:29.520 --> 0:10:32.240 the current would ionize the gas. But the other really 0:10:32.280 --> 0:10:35.720 neat thing he did was he invented a voltage multiplier 0:10:35.920 --> 0:10:39.640 circuit because he needed to generate this really high voltage 0:10:40.240 --> 0:10:43.120 around two hundred and twenty volts actually, and that could 0:10:43.160 --> 0:10:48.800 take incoming alternating current electricity. That's the type of electricity 0:10:48.880 --> 0:10:52.040 that power plants typically send out because it's easier to 0:10:52.080 --> 0:10:56.400 send out alternating current over long distances than direct current. Well, 0:10:57.240 --> 0:11:01.280 Grindacre's invention would bring in alternating current and then convert 0:11:01.280 --> 0:11:04.079 it to direct current and run the direct current through 0:11:04.120 --> 0:11:07.080 a circuit with stuff like capacitors and diodes, and the 0:11:07.080 --> 0:11:11.080 whole process is a bit complicated to explain, particularly without 0:11:11.080 --> 0:11:13.760 the use of visual aids, And also it goes beyond 0:11:14.000 --> 0:11:16.200 today's topic. But in the future I will have to 0:11:16.200 --> 0:11:20.400 talk about voltage multiplying circuits more specifically, because they are 0:11:20.440 --> 0:11:23.880 important in all sorts of technologies, including super cool bleeding 0:11:24.000 --> 0:11:27.240 edge science stuff like particle accelerators. But for the purposes 0:11:27.280 --> 0:11:29.120 of this episode, the important thing to remember is that 0:11:29.440 --> 0:11:33.839 it made it possible for Grindacher to create an ionization chamber. Now, 0:11:34.160 --> 0:11:38.120 Grinacre's concern was radioactivity, and so we're going to leave 0:11:38.200 --> 0:11:40.800 off his part of the story at this point because 0:11:41.120 --> 0:11:44.920 that was his big contribution, was creating a feasible way 0:11:44.960 --> 0:11:48.559 to make an ionization chamber. We need to focus more 0:11:48.559 --> 0:11:51.280 on the folks who actually made the first smoke detectors. 0:11:52.040 --> 0:11:54.560 Maybe I'll do a full episode about Grindacre and other 0:11:54.679 --> 0:11:57.520 early physicists in the future, since their work would lead 0:11:57.520 --> 0:12:00.840 to a deeper understanding of atomic physics and by extension, 0:12:00.920 --> 0:12:03.040 quantum physics. But for now, we're going to get back 0:12:03.080 --> 0:12:06.280 to smoke alarms. So that brings us to our next 0:12:06.320 --> 0:12:11.160 Swiss smarty pants person, Walter Jaeger. Now back in nineteen thirty, 0:12:11.600 --> 0:12:15.400 Yeager wasn't setting out to build a smoke detector. That 0:12:15.559 --> 0:12:19.480 wasn't his goal. Instead, he had developed a hypothesis. He 0:12:19.559 --> 0:12:23.400 thought that perhaps using a device with an ionization chamber 0:12:23.520 --> 0:12:26.199 like the one Grindacre had made, he could build a 0:12:26.360 --> 0:12:30.040 poison gas detector. So how did he think he could 0:12:30.080 --> 0:12:33.080 do this? Well, this gets into how smoke detectors actually work, 0:12:33.160 --> 0:12:35.880 so we're going to dive into it, all right. So, 0:12:36.080 --> 0:12:38.960 as I said before, you've got your ionized particles. That's 0:12:39.000 --> 0:12:42.319 a basic component of a large number of smoke detectors. 0:12:42.400 --> 0:12:45.160 There's actually a different type of smoke detector that doesn't 0:12:45.280 --> 0:12:48.200 use an ionization chamber at all, but i'll cover that 0:12:48.320 --> 0:12:52.560 later in this episode. So, these ionized particles are positively charged. 0:12:52.720 --> 0:12:55.120 They've had electrons stripped off of them, so they have 0:12:55.200 --> 0:12:59.920 more protons than electrons. They're positively charged. A battery can 0:13:00.280 --> 0:13:04.360 to two metal plates creates a positively charged surface on 0:13:04.360 --> 0:13:08.000 one side and a negatively charged surface on the other side. 0:13:08.320 --> 0:13:13.360 So the electrons that are stripped away from the molecules 0:13:13.679 --> 0:13:17.400 will then move to the positively charged plate, and the 0:13:17.440 --> 0:13:20.480 positive ions are going to move to the negatively charged plate. 0:13:20.520 --> 0:13:25.920 Because opposite charges attract. This movement of electrons is electricity. 0:13:25.960 --> 0:13:28.720 That's what electricity is. So it's not a lot of 0:13:28.760 --> 0:13:34.400 electrical current, but it's consistent. Jaeger hypothesized that poison gas 0:13:34.480 --> 0:13:38.959 would interfere with that current of electricity, and that if 0:13:38.960 --> 0:13:42.440 you detected a drop in current, that would set off 0:13:42.520 --> 0:13:46.720 the detector, and Jaeger would say, oh, there's poison gas here. 0:13:46.800 --> 0:13:49.480 So he started testing it, except it didn't work. The 0:13:49.520 --> 0:13:52.319 poison gas did not set off the detector, and as 0:13:52.360 --> 0:13:56.680 the story goes Yaeger was getting frustrated and stressed out 0:13:56.760 --> 0:13:59.400 and he decided to smoke a cigarette and think about 0:13:59.480 --> 0:14:02.319 the problem. And so he lights up the cigarette, he 0:14:02.360 --> 0:14:04.360 starts puffing away and the next thing he knows is 0:14:04.440 --> 0:14:07.920 detector's going off. Now, the poison gas had not interacted 0:14:07.960 --> 0:14:12.920 with the ions, but the smoke did, so what's going on. Well, 0:14:13.000 --> 0:14:16.600 there are particles in smoke that can bond to ions, 0:14:16.720 --> 0:14:21.240 neutralizing them, so negatively charged particles that can bond with 0:14:21.280 --> 0:14:24.480 the positive ones. And when that happens, you get a 0:14:24.560 --> 0:14:27.800 drop in current between those two electric plates I was 0:14:27.840 --> 0:14:31.120 talking about, and that's what sets off the detector. Another 0:14:31.160 --> 0:14:35.440 scientist named Ernst Maley improved upon this design by using 0:14:35.480 --> 0:14:39.200 a cold cathode tube. I've talked about cathode tubes in 0:14:39.240 --> 0:14:42.520 the past. Here's a quick rundown. It's essentially a device 0:14:42.560 --> 0:14:45.760 that emits electrons. Looks a lot like a light bulb. 0:14:45.800 --> 0:14:51.200 You've got a filament that's encased inside a vacuum tube, 0:14:51.360 --> 0:14:54.080 and the ideas that you pass an electric current through 0:14:54.120 --> 0:14:57.880 the cathode tube's filament. The cathode tubes filament heats up 0:14:58.000 --> 0:15:01.320 due to electrical resistance, and as it heats up, it 0:15:01.400 --> 0:15:07.520 starts to emit a stream of electrons due to thermionic emission. Essentially, 0:15:08.040 --> 0:15:12.640 that electrical resistance means that the flow gets impeded. You 0:15:12.880 --> 0:15:15.720 convert some of that energy over into heat. The heat 0:15:15.760 --> 0:15:19.600 itself strips electrons away from the tungsten filament inside, and 0:15:19.960 --> 0:15:23.520 then you get your stream. Cold cathode tubes work on 0:15:23.640 --> 0:15:28.000 a different principle, though they aren't necessarily actually cold. So 0:15:28.120 --> 0:15:33.200 you've got a cathode that's the electrode that would emit electrons, 0:15:33.760 --> 0:15:35.880 and on the opposite end of the tube you have 0:15:35.960 --> 0:15:39.520 an anode that's the side that accepts electrons. So it's 0:15:39.520 --> 0:15:44.640 the positively charged part of this particular device, and these 0:15:44.640 --> 0:15:47.800 are both sealed in a tube, and that tube also 0:15:47.880 --> 0:15:51.880 has a gas inside of it, and applying a sufficient 0:15:52.040 --> 0:15:55.480 voltage between the cathode and the anode a difference in 0:15:55.560 --> 0:16:00.000 electrical charge. If it's sufficient enough, it'll cause a discharge 0:16:00.440 --> 0:16:02.520 between the two and the gas will act as a 0:16:02.560 --> 0:16:05.600 carrier for that electrical current. So a neon light is 0:16:05.640 --> 0:16:10.800 an implementation of the cold cathode tube technology. Melee's objective 0:16:11.440 --> 0:16:14.960 was to boost the signal from the detection circuit so 0:16:15.000 --> 0:16:17.640 that the signal could be strong enough to trigger an alarm, 0:16:17.760 --> 0:16:20.880 So not just that it would detect a drop in 0:16:21.320 --> 0:16:24.520 current or a change in the electrical current across these 0:16:24.560 --> 0:16:28.000 two plates, but that it would also have a strong 0:16:28.120 --> 0:16:31.560 enough signal so it could power a loud speaker or 0:16:31.600 --> 0:16:36.800 activate a physical bell. And a separate circuit in the 0:16:36.840 --> 0:16:41.160 smoke detector activates upon this change in electrical current, sending 0:16:41.160 --> 0:16:43.600 a signal to the cold cathode tube, which acts like 0:16:43.640 --> 0:16:47.480 an amplifier. It takes that incoming signal amplifies it enough 0:16:47.480 --> 0:16:49.720 for it to do some of the useful work like 0:16:50.400 --> 0:16:53.680 powering a loud speaker and thus alerting you that there 0:16:53.800 --> 0:16:57.160 is in fact smoke in the area. Now, Jaeger, being 0:16:57.160 --> 0:17:00.400 an enterprising sort, partnered with Melee to launch a business 0:17:00.440 --> 0:17:03.600 offering smoke detectors in the late nineteen forties. However, these 0:17:03.640 --> 0:17:08.720 detectors weren't terribly practical because they required that high voltage 0:17:08.840 --> 0:17:13.200 to operate to create that ionization chamber, and homes were 0:17:13.200 --> 0:17:17.639 not wired for that kind of high voltage, so that 0:17:18.040 --> 0:17:20.720 meant that you couldn't really get one for your house. 0:17:20.760 --> 0:17:24.280 They were mostly used, again in big industrial settings where 0:17:24.320 --> 0:17:27.159 you could wire things up for that kind of power. 0:17:27.680 --> 0:17:30.720 The solution to this problem was already set in motion, 0:17:31.040 --> 0:17:34.160 though at the time it was top secret. I'll get 0:17:34.200 --> 0:17:44.520 to that after this quick break. Now, while the high 0:17:44.640 --> 0:17:48.840 voltage smoke detectors weren't seen as practical from an implementation 0:17:48.960 --> 0:17:52.719 standpoint for your average homeowner, it was undeniable that they 0:17:52.720 --> 0:17:56.000 were useful, and this was particularly highlighted in the United 0:17:56.000 --> 0:17:59.399 States by a tragedy that took place on December first, 0:17:59.520 --> 0:18:02.560 nineteen f eight, at the Roman Catholic school in Chicago 0:18:03.000 --> 0:18:07.360 called Our Lady of the Angels School. Now, the origins 0:18:07.400 --> 0:18:10.400 of the fire have never been verified. No one knows 0:18:10.480 --> 0:18:14.480 exactly what started it, but it appeared to begin in 0:18:14.560 --> 0:18:18.520 the stairwell for the school, and the school had limited 0:18:18.520 --> 0:18:21.760 fire prevention measures in place. The school itself was an 0:18:21.800 --> 0:18:25.880 older building in Chicago and had been grandfathered into Chicago's 0:18:25.960 --> 0:18:30.520 safety standards because it had previously met earlier regulations. So 0:18:30.600 --> 0:18:34.639 when the city updated its fire safety regulations, one of 0:18:34.640 --> 0:18:37.240 the policies there was that older buildings that had passed 0:18:37.280 --> 0:18:42.880 the previous ones were considered safe. Students and staff were 0:18:42.960 --> 0:18:45.680 unaware of the danger of the fire until it became 0:18:45.720 --> 0:18:49.560 a critical threat, and more than ninety children died in 0:18:49.600 --> 0:18:53.199 that tragedy. It was a truly horrifying event and it 0:18:53.280 --> 0:18:57.320 illustrated the need to develop better fire detection and prevention methods. 0:18:58.119 --> 0:19:01.600 Research in Canada and the United States began looking into 0:19:01.720 --> 0:19:06.240 various catastrophic fires that had happened over the years, and 0:19:06.280 --> 0:19:10.000 according to doctor Jim Milk of the University of Maryland, 0:19:10.280 --> 0:19:15.000 these studies found evidence suggesting that had smoke detectors been 0:19:15.040 --> 0:19:18.359 available at the time, there would have been forty percent 0:19:18.480 --> 0:19:23.119 fewer deaths in those catastrophic fires. There were more than 0:19:23.160 --> 0:19:25.600 three hundred of them that they were looking at, and 0:19:26.359 --> 0:19:29.240 rise of heat detectors, which I'll talk about in a second, 0:19:29.359 --> 0:19:33.120 would have decreased the number of fatalities less than ten percent. 0:19:33.880 --> 0:19:36.360 And these were hypotheses, mind you, there was no way 0:19:36.359 --> 0:19:39.199 of knowing that that in fact would actually have been 0:19:39.200 --> 0:19:42.000 the way it played out. We only know what actually happened, 0:19:42.000 --> 0:19:44.960 not what might have happened. But the scholars were pointing 0:19:44.960 --> 0:19:47.439 out how the cause of death wasn't always due to 0:19:47.480 --> 0:19:51.600 direct exposure to fire itself, which rise of heat detectors 0:19:51.600 --> 0:19:54.920 would help you avoid, but exposure to smoke, and smoke 0:19:54.960 --> 0:19:58.320 detectors might activate well in advance of a rise of 0:19:58.359 --> 0:20:01.760 heat detector, giving people precious time to evacuate a building. 0:20:02.480 --> 0:20:05.359 So that rise of heat detector, that's like the kind 0:20:05.359 --> 0:20:07.760 I was talking about at the top of this episode. 0:20:07.880 --> 0:20:12.840 It's the type that can monitor increases in temperature and 0:20:12.960 --> 0:20:16.560 at a certain temperature they'll activate, they'll sound an alarm, 0:20:17.000 --> 0:20:19.119 but by then it might be too late. So the 0:20:19.200 --> 0:20:22.840 high voltage requirement for smoke detectors that ionized air that 0:20:22.960 --> 0:20:26.480 had an ionization chamber was still a problem at this point. 0:20:26.600 --> 0:20:30.119 It made them impractical and expensive, particularly for homeowners. It 0:20:30.280 --> 0:20:33.080 was again more common for really big buildings like manufacturing 0:20:33.119 --> 0:20:36.000 plants and factories and that kind of thing, and the 0:20:36.080 --> 0:20:38.280 rise of heat detectors like the ones I first described 0:20:38.280 --> 0:20:40.480 in this episode would also be used in those facilities. 0:20:40.680 --> 0:20:43.440 So the solution to this problem of requiring high voltage 0:20:43.560 --> 0:20:46.199 would have its roots in a top secret program that 0:20:46.240 --> 0:20:49.720 had a very different aim. See back in nineteen forty four, 0:20:50.080 --> 0:20:52.760 there was a guy named Glenn Seborg who had been 0:20:52.800 --> 0:20:57.359 asked to join the highly classified Manhattan Project. Now, this was, 0:20:57.440 --> 0:21:01.720 of course, the United States's effort to find a way 0:21:01.760 --> 0:21:05.399 to weaponize atomic energy, to split the atom to release 0:21:05.440 --> 0:21:09.199 an enormous and destructive force that could be used as 0:21:09.200 --> 0:21:13.440 a weapon. Seborg led a team that researched radioactive materials 0:21:13.760 --> 0:21:16.080 as they tried to determine which of them would be 0:21:16.119 --> 0:21:19.320 the most useful in a weapon like an atomic bomb. 0:21:19.800 --> 0:21:23.840 They discovered and created numerous radioactive elements in the process. 0:21:24.440 --> 0:21:27.399 Elements that are above ninety two on the elemental table 0:21:27.720 --> 0:21:31.119 were all synthetic. They were all created in labs and 0:21:31.200 --> 0:21:35.320 their very unstable atoms. Now, among the ones that they 0:21:35.320 --> 0:21:40.280 worked on was one called amerasrium. So ameraserium is a 0:21:40.400 --> 0:21:45.760 synthetic element that was produced in the lab in a 0:21:45.800 --> 0:21:50.200 cyclotron experiment in Berkeley, California. The specific variant that we're 0:21:50.240 --> 0:21:53.960 interested in for this podcast is an isotope of amerasyrium. 0:21:54.000 --> 0:21:57.200 It's ameraserrium two forty one. And you know I mentioned 0:21:57.240 --> 0:22:00.760 what ions are, but what is an isotope case it's 0:22:00.760 --> 0:22:03.439 been a while since you've had basic science because I 0:22:03.440 --> 0:22:05.680 always have to look these up. I'm not trying to 0:22:05.680 --> 0:22:08.760 shame anybody. I get my stuff mixed up, so I 0:22:08.760 --> 0:22:10.600 got to look it up. Well. You know, an ion 0:22:10.680 --> 0:22:13.640 is an atom or molecule that has a net electric charge, right. 0:22:13.720 --> 0:22:16.000 That means it either has too many or too few 0:22:16.080 --> 0:22:18.720 electro electrons for it to balance out with the protons. 0:22:19.200 --> 0:22:23.480 That's an ion. Isotopes are different. You have the right 0:22:23.560 --> 0:22:27.040 number of protons and electrons, but you have different numbers 0:22:27.040 --> 0:22:32.400 of neutrons between two different two or more different variants 0:22:32.400 --> 0:22:36.520 of the same element. So ameraserrium two forty one and 0:22:36.560 --> 0:22:40.440 a marasyrium two forty two are nearly identical. They have 0:22:40.480 --> 0:22:42.959 the same number of protons and the same number of electrons, 0:22:43.160 --> 0:22:47.479 but ameraserrium two forty two has one neutron more than 0:22:47.520 --> 0:22:51.560 a maraserrium two forty one. It changes the atomic mass 0:22:52.119 --> 0:22:55.520 of that particular atom, but otherwise as the same protons 0:22:55.520 --> 0:22:59.760 and electrons as the other isotopes of that element. So 0:23:00.000 --> 0:23:03.920 the maracerrium two forty one is radioactive, which means it 0:23:04.080 --> 0:23:08.960 decays and gives off radiation. It's ionic radiation, so that 0:23:09.080 --> 0:23:12.520 means that the energy that's given off, the radiation that's 0:23:12.560 --> 0:23:16.280 given off is energetic enough to strip electrons off of 0:23:16.320 --> 0:23:20.560 atoms or molecules and ionizing them. A small amount of 0:23:20.600 --> 0:23:23.919 a maraserrium two forty one will ionize atoms like oxygen 0:23:23.960 --> 0:23:27.719 and nitrogen, just through the natural process of radioactive decay. 0:23:28.280 --> 0:23:30.560 So what do I mean by a small amount. I'm 0:23:30.560 --> 0:23:34.840 talking about one five thousandth of a gram, so a 0:23:35.080 --> 0:23:41.680 super tiny amount of radioactive material. Now, smoke detector manufacturers 0:23:41.720 --> 0:23:44.879 did not immediately jump on a maraserium as a replacement 0:23:44.960 --> 0:23:48.480 for a high voltage circuit. That would take some time 0:23:48.680 --> 0:23:51.920 and a lot of study before determining that a maraserrium 0:23:52.080 --> 0:23:56.200 was pretty safe to use under specific parameters. The type 0:23:56.240 --> 0:24:00.960 of radiation gives off is primarily alpha radiation. There's alpha, beta, 0:24:01.000 --> 0:24:03.720 and gamma radiation. I'll talk more about that in a 0:24:03.760 --> 0:24:08.560 subsequent episode, but alpha radiation is the emission of alpha particles, 0:24:08.840 --> 0:24:11.560 and an alpha particle is essentially the same thing as 0:24:11.600 --> 0:24:17.040 a helium nucleus. The nucleus of a helium atom includes 0:24:17.080 --> 0:24:20.800 two protons and two neutrons. That's an alpha particle two 0:24:20.800 --> 0:24:25.919 protons and two neutrons. An alpha particle has good ionization power, 0:24:26.480 --> 0:24:29.840 but it also doesn't have a lot of penetrative power. 0:24:29.880 --> 0:24:34.640 It can't go through matter very easily. It's a massive 0:24:34.720 --> 0:24:38.320 particle in the grand scheme of things and moves more 0:24:38.320 --> 0:24:42.040 slowly than other types of radiation, so an alpha particle 0:24:42.119 --> 0:24:44.719 is too weak to pass through a thin sheet of paper. 0:24:45.040 --> 0:24:47.560 It can only go through a few centimeters of air 0:24:48.200 --> 0:24:51.880 before it loses energy and can't move anymore. So while 0:24:51.880 --> 0:24:56.280