Speaker 1: Welcome to tex Stuff, a production of I Heart Radios
Speaker 1: How Stuff Works. Hey there, and welcome to tex Stuff.
Speaker 1: I'm your host, Jonathan Strickland. I'm an executive producer with
Speaker 1: I Heart Radio and a love of all things tech.
Speaker 1: And you know, recently guys that did episodes about how
Speaker 1: matches work and how lighters work and talked about how
Speaker 1: chemists and physicists and inventors were able to make it
Speaker 1: easier than ever to light a fire. So I thought
Speaker 1: it's really only fitting if I do an episode about
Speaker 1: smoke detectors and smoke alarms and and other types of
Speaker 1: fire alarms to talk about their history and how they work. Now, clearly,
Speaker 1: smoke detectors are incredibly important because we all know fires
Speaker 1: can be life threatening. They can spread quickly, they can
Speaker 1: cut off potential escape routes for the people who are
Speaker 1: caught in the way. So early warning systems that can
Speaker 1: alert us to danger before it becomes a mortal danger
Speaker 1: are fantastic inventions. And there are a couple of inventions
Speaker 1: I want to talk about before we actually get to
Speaker 1: smoke detectors. I'm sure that doesn't come as a surprise
Speaker 1: to any of you who have listened to tech stuff
Speaker 1: episodes before, I always like to set the ground. Well,
Speaker 1: the first one that I want to talk about is
Speaker 1: the portable electric fire alarm, as in a fire alarm
Speaker 1: that works on electricity, not a fire alarm that detects
Speaker 1: electric fires. Francis Robbins Upton, who was a physicist who
Speaker 1: was a partner and general manager of the Edison lamp works,
Speaker 1: you know as in Thomas Edison, developed this particular invention
Speaker 1: back in eight Now. According to the patent, the design
Speaker 1: would sound an alarm after detecting that the temperature had
Speaker 1: risen above some predetermined limit, so if it got too hot,
Speaker 1: this thing would go off. And the way this would
Speaker 1: work was really clever. You can actually learn exactly how
Speaker 1: it was supposed to work based on the patent that
Speaker 1: Upton got on this particular invention. So the way it
Speaker 1: works is that the there are a pair of electrical
Speaker 1: contacts and if they are in in contact with each other,
Speaker 1: if they touch each other, it completes a circuit. But
Speaker 1: normally there's a gap between them. An electricity can't pass
Speaker 1: between the two that it can't cross that gap, so
Speaker 1: it's normally in the off position. However, one of those
Speaker 1: two electrical contacts is mounted on a fixed arm and
Speaker 1: the other is on an arm that's attached to a
Speaker 1: coil of bimetallic material. Now, I mentioned bimetallic strips in
Speaker 1: the episode about lighters, and it's something you find in
Speaker 1: a lot of different technologies that depend upon changes in
Speaker 1: temperature as a variable, like thermostats have bimetallic strips in them.
Speaker 1: And essentially what it is is a strip of metal
Speaker 1: that insists of two different metals. And think of it
Speaker 1: as like a metal sandwich, a top side and a
Speaker 1: bottom side, and one metal is the top side, the
Speaker 1: other metal is the bottom side, and each metal has
Speaker 1: slightly different properties, and one of those properties is how
Speaker 1: quickly they expand when they're heated up. You know, we
Speaker 1: know that metal expands as it gets warmer. While using
Speaker 1: a bimetallic strip, you have one side that will expand
Speaker 1: faster than the other side, and when that happens, it
Speaker 1: causes the strip to curl, so it deforms as it
Speaker 1: gets warmer, one side is expanding faster than the other
Speaker 1: and you get this curled metal as a result. So
Speaker 1: with Upton's proposed invention in the patent, this coil of
Speaker 1: bimetallic material would act as sort of an actuator. As
Speaker 1: it would get warm, it would expand and this in
Speaker 1: turn would create a pushing force on the arm with
Speaker 1: the electrical contact on it that then can move toward
Speaker 1: the other electrical contact that's in a fixed position. And
Speaker 1: so once the coil had expanded enough, the two contacts
Speaker 1: would touch one another and it would complete a circuit.
Speaker 1: At that point, electrical current could actually flow from a
Speaker 1: battery that was connected to this device all the way
Speaker 1: through to activate an alarm bell. So once the temperature
Speaker 1: got hot enough the two contacts touch, you get a circuit.
Speaker 1: The alarm bell goes off. If it cools down, the
Speaker 1: contacts will slowly separate, and eventually they'll separate enough where
Speaker 1: that electrical circuit can't be complete anymore. The alarm bell
Speaker 1: would go off. And Upton's invention was, without a doubt,
Speaker 1: a very clever one, and it could help save property
Speaker 1: by sounding an alarm before a fire had raged completely
Speaker 1: out of control. But there are many dangers with fires,
Speaker 1: and heat is just one of them. Another very serious
Speaker 1: danger is smoke, which not only a scares your vision,
Speaker 1: but it also can suffocate you as well. So while
Speaker 1: the alarm as design would work, it wouldn't necessarily be
Speaker 1: enough to save lives, or it might not save enough lives,
Speaker 1: because it would only go into action after the temperature
Speaker 1: had already increased enough to make this bimetallic strip expand
Speaker 1: to a sufficient degree, and by that time it might
Speaker 1: already be too late for the people in that building. Now,
Speaker 1: as far as I know, Edison's company didn't actually produce
Speaker 1: any of these fire alarms, but they did patent it.
Speaker 1: Over in Great Britain, there was a fellow named George
Speaker 1: Andrew Darby who patented his own fire alarm, also triggered
Speaker 1: by an increase in temperature. But Darby's invention did not
Speaker 1: depend upon bimetallic strips. It depended on butter for some
Speaker 1: other material that melts at higher temperatures. Say what, all right,
Speaker 1: So imagine you've got a see saw like contraption, a
Speaker 1: lever in other words, and the heavy end of the
Speaker 1: lever uh is up in the air actually because you
Speaker 1: have a weight on the opposite end of that lever.
Speaker 1: So it's like a kid sitting on a seesaw that
Speaker 1: doesn't have another kid at the end of it. The
Speaker 1: kid at the end of the seesaw weighs it down
Speaker 1: and the free end of the seesaws up in the
Speaker 1: air well in this case, the fire alarms seesaw. The
Speaker 1: arm that's up in the air has an electrical contact
Speaker 1: point on it, and if the arm of the seesaw
Speaker 1: were to come down, that contact would complete a circuit,
Speaker 1: and thus electricity would be able to run from a
Speaker 1: battery through an alarm, very much like Upton's invention. So
Speaker 1: weighing down the other end of the arm, the thing
Speaker 1: that's actually keeping the electrical contact up in the air
Speaker 1: is a block of butter or fat or wax or
Speaker 1: some other material that can melt at higher temperatures. So
Speaker 1: as the temperature rises, the block begins to melt away,
Speaker 1: and eventually it melts enough so that the weight isn't
Speaker 1: sufficient to keep the other end of the seesaw up
Speaker 1: in the air, and it'll sink down and the contact
Speaker 1: will complete the circuit and the alarm will go off.
Speaker 1: I was amused to find a butter based fire alarm.
Speaker 1: I wasn't surprised that it came out of England, but
Speaker 1: I was amused to find it. I can think of
Speaker 1: a few potential problems with such an arrangement. For example,
Speaker 1: it might start attracting pests that could eat the weight.
Speaker 1: So in those cases you wouldn't actually have a fire alarm,
Speaker 1: but you might have a rat alarm, or it would
Speaker 1: just turn rancid and smell awful. It's still a pretty
Speaker 1: clever approach, but not one that I think you would
Speaker 1: actually want to put in your buildings. But these solutions
Speaker 1: weren't practical for homes or anything like that. As I mentioned,
Speaker 1: they wouldn't really alert you to the presence of smoke,
Speaker 1: which on its own would be enough to be deadly.
Speaker 1: So this was really looked at as more of a
Speaker 1: solution for things like factories facilities, where you've got a
Speaker 1: lot of industrial operations going on, where the risk of
Speaker 1: fire is high and the risk of property loss is
Speaker 1: also high. Smoke detectors also trace their history back to chemists, physicists,
Speaker 1: and inventors, and in fact, you could say that smoke
Speaker 1: detectors were made possible not just through exploratory science, but
Speaker 1: also happy accidents. And will begin with a super smart
Speaker 1: Swiss physicist in the early twentieth century and try saying
Speaker 1: that three times fast super smart Swiss physicist. His name
Speaker 1: was Heinrich Grinaker and Grindeker or grind Acre if you prefer,
Speaker 1: studied a lot of different stuff, including radioactivity. Vilhelm Rindken
Speaker 1: had discovered the existence of X rays in and Grindeker
Speaker 1: devoted a good deal of his work toward getting a
Speaker 1: better understanding of X rays and other forms of radiation,
Speaker 1: and to do that he had to overcome some practical obstacles.
Speaker 1: For example, he needed a device to help measure the
Speaker 1: intensity of X rays, and such a device didn't really
Speaker 1: exist yet, so he got to work inventing one. X
Speaker 1: rays are a type of ionizing radiation that means that
Speaker 1: when they encounter molecules or atoms, they can ionize them.
Speaker 1: And an ion is a molecule or an atom that
Speaker 1: has a net electrical charge, So it's either a positive
Speaker 1: particle or a negative particle. And a positive ion is
Speaker 1: one that has more protons than electrons, so you have
Speaker 1: a net positive charge. A negative ion would be the opposite,
Speaker 1: has more electrons than protons and has a net negative charge. Now,
Speaker 1: one thing Grineker did was to create ions by building
Speaker 1: a grid of wires through which he could stream high
Speaker 1: voltage current and you would pass air molecules essentially through
Speaker 1: this grid, and the current would strip electron off of
Speaker 1: those particles, creating positive ions. So the grid was in
Speaker 1: this chamber through which gas could move, and as I said,
Speaker 1: the current would ionize the gas. But the other really
Speaker 1: neat thing he did was he invented a voltage multiplier
Speaker 1: circuit because he needed to generate this really high voltage
Speaker 1: around two twenty volts actually, and that could take incoming
Speaker 1: alternating current electricity. That's the type of electricity that power
Speaker 1: plants typically send out because it's easier to send out
Speaker 1: alternating current over long distances than direct current. Well, Grindaker's
Speaker 1: invention would bring in alternating current and then convert it
Speaker 1: to direct current and run the direct current through a
Speaker 1: circuit with stuff like capacitors and diodes. And the whole
Speaker 1: process is a bit complicated to explain, particularly without the
Speaker 1: use of visual aids, and also it goes beyond today's topic.
Speaker 1: But the future I will have to talk about voltage
Speaker 1: multiplying circuits more specifically, because they are in and in
Speaker 1: all sorts of technologies, including super cool bleeding edge science
Speaker 1: stuff like particle accelerators. But for the purposes of this episode,
Speaker 1: The important thing to remember is that it made it
Speaker 1: possible for Grindeker to create an ionization chamber. Now, Greennecker's
Speaker 1: concern was radioactivity, and so we're gonna leave off his
Speaker 1: part of the story at this point because that was
Speaker 1: his big contribution, was creating a feasible way to make
Speaker 1: an ionization chamber. We need to focus more on the
Speaker 1: folks who actually made the first smoke detectors. Uh. Maybe
Speaker 1: I'll do a full episode about Grienneker and other early
Speaker 1: physicists in the future, since their work would lead to
Speaker 1: a deeper understanding of atomic physics and by extension, quantum physics.
Speaker 1: But for now, we're going to get back to smoke alarms.
Speaker 1: So that brings us to our next Swiss smarty pants person,
Speaker 1: Valter Yeager. Now, back in n Yeager wasn't setting out
Speaker 1: to build a smoke detector. That wasn't his goal. Instead,
Speaker 1: he had developed a hypothesis. He thought that perhaps using
Speaker 1: a device with an ionization chamber like the one grind
Speaker 1: Acre had made, he could build a poison gas detector.
Speaker 1: So how did he think he could do this? Well,
Speaker 1: this gets into how smoke detectors actually work. So we're
Speaker 1: going to dive into it. All right, So, as I
Speaker 1: said before, you've got your ionized particles. That's a basic
Speaker 1: component of a large number of smoke detectors. There's actually
Speaker 1: a different type of smoke detector that doesn't use an
Speaker 1: ionization chamber at all, but i'll cover that later in
Speaker 1: this episode. So, these ionized particles are positively charged. They've
Speaker 1: had electrons stripped off of them, so they have more
Speaker 1: protons than electrons. They're positively charged. A battery connected to
Speaker 1: two metal plates creates a positively charged surface on one
Speaker 1: side and a negatively charged surface on the other side.
Speaker 1: So the electrons that are stripped away from the molecules
Speaker 1: will then move to the positively charged plate and the
Speaker 1: positive ions are going to move to the negatively charged plate.
Speaker 1: But has opposite charges attract this movement of electrons is electricity.
Speaker 1: That's what electricity is. So it's not a lot of
Speaker 1: electrical current, but it's consistent. Yeager hypothesized that poison gas
Speaker 1: would interfere with that current of electricity, and that if
Speaker 1: you detected a drop in current, that would set off
Speaker 1: the detector, and Yeager would say, oh, there's poison gas here.
Speaker 1: So he started testing it accept it didn't work. The
Speaker 1: poison gas did not set off the detector. And as
Speaker 1: the story goes, Yeager was getting frustrated and stressed out
Speaker 1: and he decided to smoke a cigarette and think about
Speaker 1: the problem. And so he lights up the cigarette. He
Speaker 1: starts puffing away, and the next thing he knows is
Speaker 1: detectors going off. Now, the poison gas had not interacted
Speaker 1: with the ions, but the smoke did, So what's going on. Well,
Speaker 1: there are particles in smoke that can bond to ions,
Speaker 1: neutralizing them, So negatively charged particles that can bond with
Speaker 1: the positive ones. And when that happens, you get a
Speaker 1: drop in current between those two electric plates I was
Speaker 1: talking about, and that's what sets off the detector. Another
Speaker 1: scientist named Ernst Maine improved upon this design by using
Speaker 1: a cold cathode tube. I've talked about cathode tubes in
Speaker 1: the past. Here's a quick rundown. It's essentially a device
Speaker 1: that emits electrons. Looks a lot like a lightbulb. You've
Speaker 1: got a a filament that's encased inside a vacuum tube,
Speaker 1: and the ideas that you pass an electric current through
Speaker 1: the cathode tubes filament the cathode tubes filament heats up
Speaker 1: due to electrical resistance, and as it heats up, it
Speaker 1: starts to emit a stream of electrons due to thermionic emission. Essentially,
Speaker 1: that electrical resistance means that the flow gets impeded. You
Speaker 1: convert some of that energy over into heat. The heat
Speaker 1: itself strips electrons away from the tungusten filament inside, and
Speaker 1: then you get your dream. Cold cathode tubes work on
Speaker 1: a different principle, though they aren't necessarily actually cold. So
Speaker 1: you've got a cathode that's the electrode that would emit electrons,
Speaker 1: and on the opposite end of the tube you have
Speaker 1: an anode that's the side that accepts electron. So it's
Speaker 1: the positively charged part of this particular device. And these
Speaker 1: are both sealed in a tube, and that tube also
Speaker 1: has a gas inside of it, and applying a sufficient
Speaker 1: voltage between the cathode and the anode a difference in
Speaker 1: electrical charge. If it's sufficient enough, it will cause a
Speaker 1: discharge between the two and the gas will act as
Speaker 1: a carrier for that electrical current. So a neon light
Speaker 1: is an implementation of the cold cathode tube technology. Malee's
Speaker 1: objective was to boost the signal from the detection circuit
Speaker 1: so that the signal could be strong enough to trigger
Speaker 1: an alarm, so not just that would detect a drop
Speaker 1: in current or a change in the electrical current across
Speaker 1: these two plates, but that it would also have a
Speaker 1: strong enough signal so it could power allowed speaker or
Speaker 1: activate a physical bell. And a separate circuit in the
Speaker 1: smoke detector activates upon this change in electrical current, sending
Speaker 1: a signal to the cold cathode tube, which acts like
Speaker 1: an amplifier. It takes that incoming signal amplifies it enough
Speaker 1: for it to do some of the useful work like
Speaker 1: powering allowed speaker and thus alerting you that there is
Speaker 1: in fact smoke in the area. Now. Yeager, being an
Speaker 1: enterprising sort, partnered with Maine to launch a business offering
Speaker 1: smoke detectors in the late nineteen forties. However, these detectors
Speaker 1: weren't terribly practical because they required that high voltage to
Speaker 1: operate to to create that ionization chamber, and homes were
Speaker 1: not wired for that kind of high voltage, so that
Speaker 1: meant that you couldn't really get one for your house.
Speaker 1: They were mostly used again in big industrial settings where
Speaker 1: you could wire things up for that kind of power.
Speaker 1: The solution to this problem was already set in motion,
Speaker 1: though at the time it was top secret. I'll get
Speaker 1: to that after this quick break. Now, while the high
Speaker 1: voltage smoke detectors weren't seen as practical from an implementation
Speaker 1: standpoint for your average homeowner, it was undeniable that they
Speaker 1: were useful, and this was particularly highlighted in the United
Speaker 1: States by a tragedy that took place on December one,
Speaker 1: ninety eight at the Roman Catholic School of Chicago, called
Speaker 1: Our Lady of the Angels School. Now, the origins of
Speaker 1: the fire have never been verified. No one knows exactly
Speaker 1: what started it, but it appeared to begin in the
Speaker 1: stairwell for the school, and the school had limited fire
Speaker 1: prevention measures in place. The school itself was an older
Speaker 1: building in Chicago and had been grandfathered into Chicago's safety
Speaker 1: standards because it had previously met earlier regulations. So when
Speaker 1: the city updated its fire safety regulations, one of the
Speaker 1: policies there was that older buildings that had passed the
Speaker 1: previous ones were considered safe. Students and staff were unaware
Speaker 1: of the danger of the fire until it became a
Speaker 1: critical threat, and more than ninety children died in that tragedy.
Speaker 1: It was a truly horrifying event and it illustrated the
Speaker 1: need to develop better fire detection and prevention methods. Research
Speaker 1: in Canada and the United States began looking into various
Speaker 1: catastrophic fires that had happened over the years, and according
Speaker 1: to doctor Jim Milkey of the University of Maryland, these
Speaker 1: studies found evidence suggesting that had smoke detectors been available
Speaker 1: at the time, there would have been fewer deaths in
Speaker 1: those catastrophic fires. Uh, there were more than three hundred
Speaker 1: of them that they were looking at, and rise of
Speaker 1: heat detectors, which I'll talk about in a second, would
Speaker 1: have decreased the number of fatalities less than ten. And
Speaker 1: these were hypotheses, mind you, you there's no way of
Speaker 1: knowing that that in fact would actually have been the
Speaker 1: way it played out. We only know what actually happened,
Speaker 1: not what might have happened. But the scholars were pointing
Speaker 1: out how the cause of death wasn't always due to
Speaker 1: direct exposure to fire itself, which rise of heat detectors
Speaker 1: would help you avoid, but exposure to smoke, and smoke
Speaker 1: detectors might activate well in advance of a rise of
Speaker 1: heat detector, giving people precious time to evacuate a building.
Speaker 1: So that rise of heat detector, that's like the kind
Speaker 1: I was talking about at the top of this episode.
Speaker 1: It's the type that can uh monitor increases in temperature
Speaker 1: and at a certain temperature they'll activate, they'll sound an alarm,
Speaker 1: but by then it might be too late. So the
Speaker 1: high voltage requirement for smoke detectors that ionized air that
Speaker 1: had an ionization chamber was still a problem at this point.
Speaker 1: They made them impractical and expensive, particularly for homeowners. It
Speaker 1: was again more common for really big buildings like manufacturing
Speaker 1: plants and factories and that kind of thing, and the
Speaker 1: rise of heat detectors like the ones I first described
Speaker 1: in this episode would also be used in those facilities.
Speaker 1: So the solution to this problem of requiring high voltage
Speaker 1: would have its roots in a top secret program that
Speaker 1: had a very different aim seem Back in ninety there
Speaker 1: was a guy named Glenn Seaborg who had been asked
Speaker 1: to join the highly classified Manhattan Project. Now this was,
Speaker 1: of course, the United States effort to find a way
Speaker 1: to weaponize atomic energy to split the atom to release
Speaker 1: an enormous and destructive force that could be used as
Speaker 1: a weapon. Seaborg led a team that researched radioactive materials
Speaker 1: as they tried to determine which of them would be
Speaker 1: the most useful in a weapon like an atomic bomb.
Speaker 1: They discovered in numerous radioactive elements in the process, elements
Speaker 1: that are above ninety two on the elemental table. We're
Speaker 1: all synthetic. They were all created in labs, and they're
Speaker 1: very unstable atoms now. Among the ones that they worked
Speaker 1: on was one called amerasirium. So a Mera sirium is
Speaker 1: a synthetic h element that was produced in the lab
Speaker 1: in a cyclotron experiment in Berkeley, California. The specific variant
Speaker 1: that we're interested in for this podcast is an isotope
Speaker 1: of a Mera cirium. It's a Mera cirium too forty one.
Speaker 1: And you know I mentioned what ions are, but what
Speaker 1: is an isotope in case it's been a while since
Speaker 1: you've had basic science. Because I always have to look
Speaker 1: these up. I'm not trying to shame anybody. I I
Speaker 1: get my stuff mixed up, so I gotta look it up. Well.
Speaker 1: You know, an ion is an atom or molecule that
Speaker 1: has a net electric charge, right, the means that either
Speaker 1: has too many or too few electron electrons for it
Speaker 1: to balance out with the protons. That's an ion. I
Speaker 1: aotopes are different. You have the the right number of
Speaker 1: protons and electrons, but you have different numbers of neutrons
Speaker 1: between two different two or more different variants of the
Speaker 1: same element. So amerasirium two forty one and a Mera
Speaker 1: sirium two forty two are nearly identical. They have the
Speaker 1: same number of protons and the same number of electrons,
Speaker 1: but a merasirium two forty two has one neutron more
Speaker 1: than a Mera cirium too forty one. It changes the
Speaker 1: atomic mass of that particular atom, but otherwise as the
Speaker 1: same protons and electrons as the other isotopes of that element.
Speaker 1: So a Mera cirium to forty one is radioactive, which
Speaker 1: means it decays and gives off radiation. It's ionic radiation,
Speaker 1: so that means that the energy that's given off, the
Speaker 1: radiation that's given off is energetic enough to strip electrons
Speaker 1: off of atoms or molecules and ionizing them. A small
Speaker 1: amount of amerasium to forty one will ionize atoms like
Speaker 1: oxygen and nitrogen just through the natural process of radioactive decay.
Speaker 1: So what do I mean by a small amount. I'm
Speaker 1: talking about one five thousand of a gram, so a
Speaker 1: super tiny amount of radioactive material. Now, smoke detector manufacturers
Speaker 1: did not immediately jump on a mera cirium as a
Speaker 1: replacement for a high voltage circuit. That would take some
Speaker 1: time and a lot of study before determining that amerasirium
Speaker 1: was pretty safe to use under specific parameters. The type
Speaker 1: of radiation gives off is primarily alpha radiation. There's alpha, beta,
Speaker 1: and gamma radiation. I'll talk more about that in a
Speaker 1: subsequent episode. But alpha radiation is the emission of alpha particles,
Speaker 1: and an alpha particle is essentially the same thing as
Speaker 1: a helium UH nucleus. UH. The nucleus of a helium
Speaker 1: atom includes two protons and two neutrons. That's an alpha
Speaker 1: particle two protons and two neutrons. An alpha particle has
Speaker 1: good ionization power, but it also doesn't have a lot
Speaker 1: of penetrative power. It can't go through matter very easily.
Speaker 1: It's a massive particle in the grand scheme of things
Speaker 1: UH and moves more slowly than other types of radiation.
Speaker 1: So an alpha particle is too weak to pass through
Speaker 1: a thin sheet of paper. It can only go through
Speaker 1: a few centimeters of air before it loses energy and
Speaker 1: can't move anymore. So, while embarrass serrium to forty one
Speaker 1: is radioactive, it's considered relatively safe in small amounts, and
Speaker 1: if kept in isolation. You wouldn't want to come into
Speaker 1: direct contact with the stuff. And you definitely wouldn't want
Speaker 1: to inhale or ingest any emiss cerium or get it
Speaker 1: in an open wound because it is carcinogenic. But it
Speaker 1: would have to get past barriers. It's not even strong
Speaker 1: enough to get through the skin, but it is strong
Speaker 1: enough if you were to ingest or breathe in some dust,
Speaker 1: it could potentially cause cancer. It could certainly increase your
Speaker 1: risk of developing cancer. So there is a danger to it.
Speaker 1: So your typical smoke detector actually has some radioactive material
Speaker 1: in it to create the ions that flow between two
Speaker 1: charged plates. The ions behave just as the ones did
Speaker 1: with Yeager's high voltage device. It's the same source stuff.
Speaker 1: It's charged particles, So smoke particles will still interact with them,
Speaker 1: just as they would with Yeager's invention with the high
Speaker 1: voltage grid, and they will still bind and cause a
Speaker 1: drop in current, and that's what triggers the circuit that
Speaker 1: powers the actual alarm. Now, it would be nearly two
Speaker 1: decades between the invention of amerasirium two forty one and
Speaker 1: its application as an ion generator in a smoke detector.
Speaker 1: The United States Atomic Energy Commission would grant a license
Speaker 1: in nineteen sixty three authorizing the use of a Merra
Speaker 1: cirium to forty one in smoked at hectors. And the
Speaker 1: thought was that the amount of radioactive material that would
Speaker 1: be so tiny that, uh, it would not really stand
Speaker 1: to be a hazard, and it's just a very low risk.
Speaker 1: But there was a very real risk of fire and smoke.
Speaker 1: And so when you weighed it against each other and
Speaker 1: said the risk of fire is high and the risk
Speaker 1: of something happening because of this very tiny amount of
Speaker 1: radioactive material is low, it makes way more sense to
Speaker 1: air on the side of detecting fires. So two years later,
Speaker 1: in a guy named Dwayne d Personal introduced a battery
Speaker 1: powered smoke detector. This eliminated the need for that high
Speaker 1: voltage circuit, and Personal came by this accidentally. A lot
Speaker 1: of inventions really end up being created as a consequence
Speaker 1: of some other unrelated effort. So in nineteen sixty three,
Speaker 1: that same year where the Atomic Energy Commission granted the license,
Speaker 1: Personal had been working on some tough problems with his employees.
Speaker 1: Not problems with his employees, but with his employees. They
Speaker 1: were working on tough problems. Personal was in a rough spot,
Speaker 1: so he had taken out a second mortgage on his
Speaker 1: house to create a company called Personal Company and a
Speaker 1: spinoff company called Satra. To all are Sata Troll rather
Speaker 1: Santatoral Corporation in Denver, Colorado. Uh I find that name
Speaker 1: incredibly difficult to say properly. In fact, I'm sure I'm
Speaker 1: saying it incorrectly. But anyway, the company's main business was
Speaker 1: selling heating and air distribution equipment for commercial buildings, so
Speaker 1: sort of like an HVAC company for big, big, big buildings.
Speaker 1: But the products his engineers were working on was what
Speaker 1: he called a static neutralizer. The idea was he was
Speaker 1: going to create an ion generator, and the idea was
Speaker 1: that these ions would neutralize static electricity build up on equipment,
Speaker 1: and that's something that could be a real issue for
Speaker 1: industrial operations and clean rooms and stuff. So you need
Speaker 1: to have a way to new trill eyes static build up,
Speaker 1: or else you can have a discharge that could ruin
Speaker 1: tons of work. However, his team had encountered a problem.
Speaker 1: They saw that their ion generator was getting clogged up
Speaker 1: pretty quickly. The ions were attracting particles like dust and stuff,
Speaker 1: and as it was attracting dust, it was starting to
Speaker 1: make the entire device as a whole less effective. An
Speaker 1: engineer named Lyman Blackwell was running tests to see what
Speaker 1: could be done to keep the ion generation going. While
Speaker 1: testing the system, they noticed that the ion meter they
Speaker 1: were using to monitor performance would occasionally fluctuate, and one
Speaker 1: of the technicians running the equipment was a smoker. He
Speaker 1: was chained smoking during the whole testing process. Eventually, they
Speaker 1: figured out that the meter was detecting fluctuations in the
Speaker 1: ion flow whenever smoke was getting pulled in through the
Speaker 1: fan on the generator and inserted into the ion stream.
Speaker 1: So essentially they were making the same discovery that Yeager
Speaker 1: had aid decades earlier, but the big difference was that
Speaker 1: Purcell's ion generator didn't require that high voltage to run
Speaker 1: because it was depending on that small amount of ameras
Speaker 1: serium to forty one. So he had the bright idea
Speaker 1: to take this unexpected result and turn it into an
Speaker 1: actual product. Two years later, he had the first battery
Speaker 1: operated ionization based smoke detector. He called it the Smoke
Speaker 1: Guard seven hundred, but it wasn't quite ready for the
Speaker 1: home market yet because government regulations had not yet caught
Speaker 1: up to the technology. We're gonna get into that as well, because,
Speaker 1: as it turns out, it's not enough just to make
Speaker 1: tech that works. You have to make tech that works
Speaker 1: within the boundaries of laws and regulations. Meanwhile, a pair
Speaker 1: of inventors named Donald Steele and Robert Emerk came up
Speaker 1: with an alternative method for detecting smoke with a with
Speaker 1: a device, And this approach wouldn't used ionized particles at all,
Speaker 1: so there's no need to create any sort of ionization chamber. Instead,
Speaker 1: Steel and m Mark created a smoke detector that relied
Speaker 1: upon light and photo detectors. So photo detectors those are
Speaker 1: that's light sensors, rights a sensor that detects light. There
Speaker 1: are two basic categories of light sensors. The first type
Speaker 1: are sometimes called photovoltaics. These are devices that emit electrons
Speaker 1: when they're exposed to light, So solar panels are a
Speaker 1: type of photovoltaic cells, uh they generate electricity when exposed
Speaker 1: to light. The other type of light sensor would be
Speaker 1: the photo resistor or photo conductor. These sensors have electrical
Speaker 1: properties that change if they are actually exposed to light. So,
Speaker 1: for example, a photo resistor has a relatively high electrical
Speaker 1: resistance when it's in the dark, so that material resists
Speaker 1: the flow of electricity going through it. However, as the
Speaker 1: material is exposed to light, the electrical resistance decreases, an
Speaker 1: electricity can pass through it more readily. So if you
Speaker 1: place one of these devices in a circuit and you
Speaker 1: have a voltage detector also attached to that circuit, the
Speaker 1: detector will pick up changes in voltage as light hits
Speaker 1: the sensor. Now, you could try and build a smoke
Speaker 1: detector that works by having a light shining on a
Speaker 1: photo sensor of some sort that's at least partially open
Speaker 1: to the air outside of the detector, and if something
Speaker 1: like smoke were to enter that pathway the direct detector's events,
Speaker 1: and it somehow gets in between the light and the sensor.
Speaker 1: Then you would have smoke obscuring or blocking some of
Speaker 1: that light, and if it were enough, then the alarm
Speaker 1: would go off. But that actually wouldn't be a very
Speaker 1: sensitive smoke detector. It wouldn't work unless the smoke was
Speaker 1: thick enough to really cause an issue. It's actually pretty
Speaker 1: tricky for a sensor to detect dips in light intensity,
Speaker 1: and by the time it would the smoke might be
Speaker 1: thick enough to already be a major threat to people's safety.
Speaker 1: But there's a clever work around to this. So instead
Speaker 1: of an alarm that goes off when a light no
Speaker 1: longer is shining on it, designer system where the alarm
Speaker 1: goes off if the sensor detects light. Even a small
Speaker 1: amount of light can create enough of a signal for
Speaker 1: it to send a message to start the alarm. So
Speaker 1: in this version, you've got a light that's shining down
Speaker 1: a pathway. So imagine a chamber. You've got a light
Speaker 1: at one end, and uh it's open, so that air
Speaker 1: can come into the chamber nine at a nine degree angle,
Speaker 1: like a perpendicular angle to this light and tucked away
Speaker 1: just a bit back. You have a little alcove where
Speaker 1: there's a sensor. So under normal conditions, the light is
Speaker 1: going through the chamber, but the sensor is tucked in
Speaker 1: at a right angle, so it's not picking up any light.
Speaker 1: The sensor stays in the dark. However, if smoke enters
Speaker 1: the chamber that the light is passing through, some of
Speaker 1: that light hits the smoke and starts to scatter. And
Speaker 1: this is the same sort of effect you would see
Speaker 1: if you were driving a car on a really foggy day.
Speaker 1: That's why you're not supposed to use the high beams
Speaker 1: on your headlights when you're in the fog. The light
Speaker 1: will hit the fog and scatter. It's more likely to
Speaker 1: make it harder for you to see rather than easier.
Speaker 1: When the smoke detector, some of that scattered light hits
Speaker 1: the sensor, which then activates a signal to the alarm.
Speaker 1: And that approach allows for far more sensitivity In a
Speaker 1: smoke detector. They can go off much faster than one
Speaker 1: that would require the smoke to block the light. So
Speaker 1: a dark sensor picking up on light is just more
Speaker 1: reliable than a lit up sensor trying to detect a
Speaker 1: dip in brightness. However, it's also not fool proof because
Speaker 1: vapor or dust could cause false alarms. Now, during all
Speaker 1: this innovation, changes were starting to happen on regulatory levels
Speaker 1: around the world. And when we come back, I'll talk
Speaker 1: more about how that played out in the United States.
Speaker 1: But first let's take an their quick break. All right,
Speaker 1: So now we've got the basic technology of smoke detectors understood,
Speaker 1: let's talk about regulations. See, if you're going to produce
Speaker 1: and market something that's meant to protect lives, it's often
Speaker 1: the case that a government agency or two will take
Speaker 1: notice and they want to make sure that the thing
Speaker 1: you're making does what you claim it does it if
Speaker 1: lives literally hang in the balance, it's important. So this
Speaker 1: is the same basic underlying philosophy we see an agencies
Speaker 1: that monitor stuff like food processing and pharmaceutical development and production.
Speaker 1: The era I'm talking about in the late nineteen sixties
Speaker 1: in the United States was a particularly tumultuous time. You
Speaker 1: had the Civil rights movement, you had America's involvement in Vietnam,
Speaker 1: and other really politically charged events playing out in the US,
Speaker 1: and these were sparks pun in tended that ignited civil
Speaker 1: unrest across the entire country, and in turn that was
Speaker 1: testing the limits of police forces and fire prevention and
Speaker 1: fire uh extinguishing services. So this prompted the US Congress
Speaker 1: to re examine policies around safety to better protect citizens.
Speaker 1: One thing to come out of this was the Fire
Speaker 1: Research and Safety Act, which was signed into law by
Speaker 1: then President Lyndon Johnson. The President was citing some figures
Speaker 1: that suggested as many as twelve thousand Americans had died
Speaker 1: in fires in nineteen sixties. Six Later estimates adjusted that
Speaker 1: number down significantly to like eight thousand, but that's still
Speaker 1: way too many people. The Act called for the creation
Speaker 1: of a twenty person panel to study the challenges and
Speaker 1: make recommendations for new safety standards that could be carried
Speaker 1: out at the federal level and require any building in
Speaker 1: the US to follow certain processes to make sure that
Speaker 1: they were safe for people. And it took a few
Speaker 1: years for all of this to actually coalesce into a report.
Speaker 1: I mean, it was a big task, and we also
Speaker 1: happen to know that things in the U. S. Government
Speaker 1: don't go super fast. But in nineteen seventy three, the
Speaker 1: panel released a report. The report was titled America Burning,
Speaker 1: which is pretty sobering all on its own, and America
Speaker 1: was leading the way in industrial nations when it came
Speaker 1: to per capita deaths and property loss due to fire.
Speaker 1: So the argument they were making was that America is
Speaker 1: this incredibly advanced country, Why the heck are we losing
Speaker 1: so much to fire? We should be doing better than that,
Speaker 1: And of the deaths were occurring in people's homes. The
Speaker 1: report also contained pictures of Person's smoke guard detector. He
Speaker 1: had come to overcome challenges to make his detector practical
Speaker 1: and safe, and his original design did not have a battery. Instead,
Speaker 1: it was to be hardwired into the electrical system of
Speaker 1: a building. It didn't require two twenty volts like the
Speaker 1: earlier smoke detectors of Switzerland did, but it still was
Speaker 1: an expensive proposition and it made it an unlikely candidate
Speaker 1: for home adoption because every unit would set someone back
Speaker 1: about a thousand dollars at the time, which would be
Speaker 1: a lot more than that today. So his team was
Speaker 1: able to create a version that would operate on battery power,
Speaker 1: which was already an engineering triumph, but they need to
Speaker 1: figure out how to make this a reliable one, or
Speaker 1: to convince people that it was reliable, because batteries, as
Speaker 1: we all know, eventually exhaust themselves. The chemical reactions inside
Speaker 1: a battery are what produces electrons, and over time you
Speaker 1: get to a point where there's been enough of the
Speaker 1: chemical reaction going on that you don't have the active
Speaker 1: ingredients necessary to sustain that that supply of electricity anymore,
Speaker 1: and not the proper voltage anyway. And we're talking about
Speaker 1: something as critical as a smoke detector, that's a real problem.
Speaker 1: So his team solved this issue by creating circuits that
Speaker 1: would send a chirping alarm to the smoke detector if
Speaker 1: it detected a drop in voltage across the primary circuit
Speaker 1: of the smoke detector. So the chirp wouldn't require very
Speaker 1: much energy of itself, and it would be repeated until
Speaker 1: the voltage across the circuit returned to the proper level,
Speaker 1: in other words, until the battery was replaced. In addition,
Speaker 1: Personal included a small card in the box for the
Speaker 1: smoke guards seven, and customers were meant to take the
Speaker 1: card and then fill out little forms on the card
Speaker 1: with their own information, including their address and the date
Speaker 1: that they installed their smoke detector, and Personal's company would
Speaker 1: actually mail out an annual reminder to its customers saying, hey,
Speaker 1: it's time for you to replace the battery and your
Speaker 1: smoke detector. In order to keep it operational. Personal worked
Speaker 1: closely with safety officials and organizations both to improve his
Speaker 1: smoke detectors and make them more useful, and also to
Speaker 1: help shape policy so that these detectors would be recognized
Speaker 1: as effective and a good option to help curb the
Speaker 1: problem of fatalities due to fire disasters, and the work
Speaker 1: paid off both for Personal and for people in general.
Speaker 1: He was able to convince officials that a battery powered
Speaker 1: smoke detector was effective if it had the ability to
Speaker 1: alert occupants of a dying battery. The government actually would
Speaker 1: mandate that the chirping alarm sound should last at least
Speaker 1: seven consecutive days in an effort to alert homeowners to
Speaker 1: change out a battery. And this was specifically in case
Speaker 1: so I might be out of town when the battery
Speaker 1: starts to give out. They wanted it to last long
Speaker 1: enough so that you would have time to get back
Speaker 1: and find out. Oh gosh, I need to switch out
Speaker 1: the batteries on my smoke detector. The government also had
Speaker 1: to balance out the cost of installing fire prevention systems
Speaker 1: and homes, including in newly constructed homes. Initially, plans called
Speaker 1: for both smoke detectors and rise of heat detectors. However,
Speaker 1: after numerous studies, the government concluded that rise of heat
Speaker 1: detectors weren't really practical if you were looking at trying
Speaker 1: to save lives. They just they just weren't good enough
Speaker 1: to do that, and they were really expensive, and that
Speaker 1: smoke detectors were much better for the purpose of preventing fatalities.
Speaker 1: And so that meant that they got rid of the
Speaker 1: rise of heat detector requirement, and that helped bring the
Speaker 1: cost down of implementing fire protection systems and homes, and
Speaker 1: that in turn increased the likelihood that people would actually
Speaker 1: follow the rules and adopt smoke detectors. The regulations paved
Speaker 1: the way for Personal to manufacture, market, and sell his
Speaker 1: smoke detectors to the American public, who could be reassured
Speaker 1: that the devices would actually provide a valuable and potentially
Speaker 1: life saving service. He scaled up his company to meet
Speaker 1: demand before eventually selling it off in nineteen seventy seven.
Speaker 1: And from everything I've read about him, it sounds like
Speaker 1: he was motivated not only by an entrepreneurial spirit, although
Speaker 1: he certainly had that, but also a genuine desire to
Speaker 1: make his community and the world a better place if
Speaker 1: he could, And I think that's pretty cool. Since the
Speaker 1: introduction of the optical and the ionization chamber based smoke detectors,
Speaker 1: we've seen some innovations, but the basic principles all remain
Speaker 1: the same. There are smoke detectors that incorporate both types
Speaker 1: of methodologies, meaning there are smoke detectors that have independent
Speaker 1: systems to detect the presence of smoke, and we've seen
Speaker 1: some incorporate other types of text such as network connectivity
Speaker 1: in the form of products like the Nest Protect smoke detector,
Speaker 1: and those smoke detectors add a little more functionality to
Speaker 1: the basic kind. They work on basically the same principle,
Speaker 1: but they have some more features. For example, they can
Speaker 1: send information across a local area network wirelessly, and then
Speaker 1: that network can send an alert to you on an
Speaker 1: app on a smartphone, and that could be valuable if,
Speaker 1: for example, you're away from your home. When an alarm
Speaker 1: goes off to give you a notification, you can perhaps
Speaker 1: either call home, or if no one's home, you might
Speaker 1: even call a fire department to go and check on
Speaker 1: your home to make sure that everything is all right.
Speaker 1: And most homes have multiple smoke detectors. In fact, you're
Speaker 1: supposed to have one outside of every bedroom, for example,
Speaker 1: as well as maybe one in the kitchen. My own
Speaker 1: home has six of the darned things, and there could
Speaker 1: be an issue of figuring out which detector is going off,
Speaker 1: and that could be of vital importance. So with connected detectors,
Speaker 1: then you get a notification saying detector number three is
Speaker 1: going off, and you know that number three happens to
Speaker 1: be outside the guest room, so you would be able
Speaker 1: to very quickly figure out what's going on, as opposed
Speaker 1: to trying to determine which of your numerous alarms is
Speaker 1: going off. It also means that if a battery is
Speaker 1: running out and a smoke detector is chure ing, or
Speaker 1: maybe a battery was just a bad battery and starts
Speaker 1: to chirp, you get more quickly track down which detector
Speaker 1: is making the chirping noise. This really applies to folks
Speaker 1: like me because I live in a townhouse that has
Speaker 1: a few floors, and the center of the townhouse is
Speaker 1: essentially like a chimney. There are stairs that go from
Speaker 1: the bottom floor, and the stairwells open all the way
Speaker 1: to the top of the town house, so it's like
Speaker 1: an echo chamber inside my house, which means when something
Speaker 1: like a smoke detector starts to chirp, I can't easily
Speaker 1: identify whether it's on the floor I'm on the floor
Speaker 1: above me or the floor below me. And I have
Speaker 1: six smoke detectors. If it's time to replace the batteries,
Speaker 1: that's one thing, But if it's just that a battery
Speaker 1: is going bad early, then I have to figure out
Speaker 1: which of those detectors is making the problem. And exacerbating
Speaker 1: this issue for me is the fact that I have
Speaker 1: a cute little doggie named Timbolt, and the chirping smoke
Speaker 1: detector noise causes him intense distress, like he starts to
Speaker 1: shake with fear. So I get really upset when one
Speaker 1: of my smoke detectors starts to chirp prematurely. There's no
Speaker 1: smoke or anything, it's just giving me a chirp alarm,
Speaker 1: but that's a me problem. One other thing that a
Speaker 1: lot of smoke detectors can do these days is they
Speaker 1: can also perform as carbon monoxide detectors. So carbon monoxide
Speaker 1: is an odorless and colorless gas, so human beings can't
Speaker 1: easily detect it, and it's also toxic. It's a byproduct
Speaker 1: from burning carbon based fuels like gasoline, heating oil, or
Speaker 1: natural gas, and in confined spaces it can be really
Speaker 1: dangerous stuff, so like a garage, for example. And while
Speaker 1: we humans can't really detect carbon monoxide with our own senses,
Speaker 1: there are a lot of other ways to see if
Speaker 1: the stuff is around. So carbon monoxide detectors can work
Speaker 1: using one of a few different methods. Upon detect action,
Speaker 1: they basically do the same thing as a smoke detector.
Speaker 1: They send a signal to sound an alarm, but the
Speaker 1: way they detect the carbon monoxide can be a little different.
Speaker 1: So there are three basic approaches to this uh and
Speaker 1: one you might have what are called bio mimetic sensors.
Speaker 1: These sensors mimic, thus the name some sort of biological functions,
Speaker 1: such as hemoglobin, which interacts with carbon monoxide. So These
Speaker 1: sensors have a gel inside of them, and that gel
Speaker 1: can absorb carbon monoxide. As the gel does absorb carbon monoxide,
Speaker 1: the gel changes color. You have a separate sensor that's
Speaker 1: monitoring the color of the gel, and if the gel changes,
Speaker 1: then the sensor picks up on that change and sends
Speaker 1: a signal to the alarm. UH. These sensors can actually
Speaker 1: be reset. The gel will return to its original color
Speaker 1: once it it gets rid of that carbon monoxide, but
Speaker 1: it has to be set in an environment that's free
Speaker 1: of carbon monoxide for several hours in order to reset.
Speaker 1: The next type is the metal oxide semiconductor sensor. This
Speaker 1: has components to have a certain level of electrical resistance,
Speaker 1: very much like the optical smoke detectors I talked about earlier.
Speaker 1: So these components react with carbon monoxide in a way
Speaker 1: that lowers the materials electrical resistance, and so meters are
Speaker 1: monitoring a voltage across a circuit and if it detects
Speaker 1: this change in voltage, then it will send a signal
Speaker 1: to the alarm. And the third type of sensor that
Speaker 1: you could find in a carbon monoxide detector is an
Speaker 1: electrochemical sensor. These sensors also detect changes an electrical current
Speaker 1: in the presence of carbon monoxide, but they have electrodes
Speaker 1: that are inside a chemical solution, so they're actually engulfed
Speaker 1: in a chemical solution around these electrodes, and the chemicals
Speaker 1: in the solution react very very quickly in the presence
Speaker 1: of carbon monox eide, and that changes the electrical qualities
Speaker 1: of the the solution, which means that you are able
Speaker 1: to detect a change in the circuit very very quickly.
Speaker 1: In fact, this stuff is used in professional settings. Uh,
Speaker 1: it's a very sensitive kind of alarm. Today, there are
Speaker 1: a lot of smoke detectors that double as carbon monoxide
Speaker 1: detectors with separate components monitoring the environment. And that's all
Speaker 1: smoke detectors work. Uh. It's a fascinating journey letting us
Speaker 1: learn a lot about physics, including nuclear physics, and we
Speaker 1: will be talking more about nuclear physics in our next episode.
Speaker 1: We'll talk about radiation and Geiger counters and uh, the
Speaker 1: discoveries that were made that really taught us all about radiation,
Speaker 1: and a lot of those discoveries came at a significant
Speaker 1: human cost. But that's an episode for our next tech stuff.
Speaker 1: This particular episode is now concluded, so if you guys
Speaker 1: have suggestions for future episodes of tech Stuff, reach out
Speaker 1: to me on social media. We are at Facebook and
Speaker 1: we are at Twitter with the handle text stuff H
Speaker 1: s W and I'll talk to you again really soon.
Speaker 1: Text Stuff is a production of I Heart Radio's How
Speaker 1: Stuff Works. For more podcasts from my heart Radio, visit
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