Speaker 1: Welcome to Tech Stuff, a production of Iheartradios How Stuff Works.
Speaker 1: Hey there, and welcome to tech Stuff. I'm your host,
Speaker 1: Jonathan Strickland. I'm an executive producer with iHeart Podcasts and
Speaker 1: how the Tech are you. Well, I'm still vacating, which
Speaker 1: means I'm off in Florida being a crazy tourist type person.
Speaker 1: And in the meantime, I have an episode for you
Speaker 1: that we publish back on February tenth, twenty twenty. This
Speaker 1: one is titled How Smoke Detectors Work. I figured it
Speaker 1: was a good idea to do an episode about smoke
Speaker 1: detectors as we go toward the end of the year,
Speaker 1: because I've always tried to change out the batteries and
Speaker 1: my smoke detectors at the beginning of each year, because
Speaker 1: otherwise I just would forget to do it. But by
Speaker 1: making it like, hey, happy New Year, you gotta change
Speaker 1: out all the smoke detector batteries, I am less likely
Speaker 1: to forget. But how did those darned things work in
Speaker 1: the first place. Well, let's listen and find out. 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 robins Upton, who is a physicist who
Speaker 1: was a partner and general manager of the Edison Lamp Works,
Speaker 1: as in Thomas Edison, developed this particular invention back in
Speaker 1: eighteen ninety. Now, according to the patent, the design would
Speaker 1: sound an alarm after detecting that the temperature had risen
Speaker 1: 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 there are a pair of electrical contacts
Speaker 1: and if they are in contact with each other, if
Speaker 1: they touch each other, it completes a circuit. But normally
Speaker 1: there's a gap between them and electricity can't pass between
Speaker 1: the two. It can't cross that gap, so it's normally
Speaker 1: in the off position. However, one of those two electrical
Speaker 1: contacts is mounted on a fixed arm and the other
Speaker 1: is on an arm that's attached to a coil of
Speaker 1: biomet hallick material. Now I mentioned biometallic strips in the
Speaker 1: episode about lighters, and it's something you find in a
Speaker 1: lot of different technologies that depend upon changes in temperature
Speaker 1: 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 consists 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. Well, 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 doubt a
Speaker 1: very clever one, and it could help save property by
Speaker 1: sounding an alarm before a fire had raged completely out
Speaker 1: of control. But there are many dangers with fires, and
Speaker 1: heat is just one of them. Another very serious danger
Speaker 1: is smoke, which not only obscures your vision, but it
Speaker 1: also can suffocate you as well. So while the alarm
Speaker 1: as design would work, it wouldn't necessarily be enough to
Speaker 1: save lives, or it might not save enough lives because
Speaker 1: it would only go into action after the temperature had
Speaker 1: already increased enough to make this bimetallic strip expand to
Speaker 1: a sufficient degree, and by that time it might already
Speaker 1: 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 or some
Speaker 1: other material that melts at higher temperatures. Say what, all right,
Speaker 1: So imagine you've got a seesaw like contraption, a lever
Speaker 1: in other words, and the heavy end of the lever
Speaker 1: is up in the air actually because you have a
Speaker 1: weight on the opposite end of that lever. So it's
Speaker 1: like a kid sitting on a seesaw that doesn't have
Speaker 1: another kid at the end of it. The kid at
Speaker 1: the end of the sea saw weighs it down, and
Speaker 1: the free end of the seesaw is up in the air. Well,
Speaker 1: in this case, the fire alarms seesaw. The arm that's
Speaker 1: up in the air has an electrical contact point on it,
Speaker 1: and if the arm of the seesaw were to come down,
Speaker 1: that contact would complete a circuit, and thus electricity would
Speaker 1: be able to run from a battery through an alarm,
Speaker 1: very much like Upton's invention. So weighing down the other
Speaker 1: end of the arm. The thing that's actually keeping the
Speaker 1: electrical contact up in the air is a block of
Speaker 1: butter or fat or wax or some other material that
Speaker 1: can melt at higher temperatures. So as the temperature rises,
Speaker 1: the block begins to melt away, and eventually it melts
Speaker 1: enough so that the weight isn't sufficient to keep the
Speaker 1: other end of the seesaw up in the air, and
Speaker 1: it'll sink down and the contact will complete the circuit
Speaker 1: and the alarm will go off. I was amused to
Speaker 1: find a butter based fire alarm. I wasn't surprised that
Speaker 1: it came out of England, but I was amused to
Speaker 1: find it. I can think of a few potential problems
Speaker 1: with such an arrangement. For example, it might start attracting
Speaker 1: pests that could eat the weight, so in those cases
Speaker 1: you wouldn't actually have a fire alarm, but you might
Speaker 1: have a rat alarm, or it would just turn rancid
Speaker 1: and smell offul Still a pretty clever approach, but not
Speaker 1: one that I think you would actually want to put
Speaker 1: in your buildings. But these solutions weren't practical for homes
Speaker 1: or anything like that. As I mentioned, they wouldn't really
Speaker 1: alert you to the presence of smoke, which on its
Speaker 1: own would be enough to be deadly. So this was
Speaker 1: really looked at as more of a solution for things
Speaker 1: like factories facilities, where you've got a lot of industrial
Speaker 1: operations going on, where the risk of fire is high
Speaker 1: and the risk of property loss is also high smoke
Speaker 1: detectors also trace their history back to chemists, physicists, and inventors,
Speaker 1: and in fact, you could say that smoke detectors were
Speaker 1: made possible not just through exploratory science, but also happy accidents.
Speaker 1: And will begin with a super smart Swiss physicist in
Speaker 1: the early twentieth century and try saying that three times fast.
Speaker 1: Super smart Swiss physicist. His name was Heinrich Grinecker or
Speaker 1: Grindacre if you prefer study a lot of different stuff,
Speaker 1: including radioactivity. Wilhelm Runtgen had discovered the existence of X
Speaker 1: rays in eighteen ninety five, and Grindacre devoted a good
Speaker 1: deal of his work toward getting a better understanding of
Speaker 1: X rays and other forms of radiation, and to do
Speaker 1: that he had to overcome some practical obstacles. For example,
Speaker 1: he needed a device to help measure the intensity of
Speaker 1: X rays, and such a device didn't really exist yet,
Speaker 1: so he got to work inventing one. X rays are
Speaker 1: a type of ionizing radiation that means that when they
Speaker 1: encounter molecules or atoms, they can ionize them. And an
Speaker 1: ion is a molecule or an atom that has a
Speaker 1: net electrical charge, so it's either a positive particle or
Speaker 1: a negative particle. And a positive ion is one that
Speaker 1: has more protons than electrons, so you have a net
Speaker 1: positive charge. A negative ion would be the opposite, has
Speaker 1: more electrons than protons and has a net negative charge. Now,
Speaker 1: one thing Grindacre 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 electrons 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 hundred and twenty volts actually, and that could
Speaker 1: take incoming alternating current electricity. That's the type of electricity
Speaker 1: that power plants typically send out because it's easier to
Speaker 1: send out alternating current over long distances than direct current. Well,
Speaker 1: Grindacre's invention would bring in alternating current and then convert
Speaker 1: it to direct current and run the direct current through
Speaker 1: a circuit with stuff like capacitors and diodes, and the
Speaker 1: whole process is a bit complicated to explain, particularly without
Speaker 1: the use of visual aids, And also it goes beyond
Speaker 1: today's topic. But in the future I will have to
Speaker 1: talk about voltage multiplying circuits more specifically, because they are
Speaker 1: important in all sorts of technologies, including super cool bleeding
Speaker 1: edge science stuff like particle accelerators. But for the purposes
Speaker 1: of this episode, the important thing to remember is that
Speaker 1: it made it possible for Grindacher to create an ionization chamber. Now,
Speaker 1: Grinacre's concern was radioactivity, and so we're going to leave
Speaker 1: off his part of the story at this point because
Speaker 1: that was his big contribution, was creating a feasible way
Speaker 1: to make an ionization chamber. We need to focus more
Speaker 1: on the folks who actually made the first smoke detectors.
Speaker 1: Maybe I'll do a full episode about Grindacre and other
Speaker 1: early physicists in the future, since their work would lead
Speaker 1: to a deeper understanding of atomic physics and by extension,
Speaker 1: quantum physics. But for now, we're going to get back
Speaker 1: to smoke alarms. So that brings us to our next
Speaker 1: Swiss smarty pants person, Walter Jaeger. Now back in nineteen thirty,
Speaker 1: Yeager wasn't setting out to build a smoke detector. That
Speaker 1: wasn't his goal. Instead, he had developed a hypothesis. He
Speaker 1: thought that perhaps using a device with an ionization chamber
Speaker 1: like the one Grindacre had made, he could build a
Speaker 1: poison gas detector. So how did he think he could
Speaker 1: do this? Well, this gets into how smoke detectors actually work,
Speaker 1: so we're going to dive into it, all right. So,
Speaker 1: as I said before, you've got your ionized particles. That's
Speaker 1: a basic component of a large number of smoke detectors.
Speaker 1: There's actually a different type of smoke detector that doesn't
Speaker 1: use an ionization chamber at all, but i'll cover that
Speaker 1: later in this episode. So, these ionized particles are positively charged.
Speaker 1: They've had electrons stripped off of them, so they have
Speaker 1: more protons than electrons. They're positively charged. A battery can
Speaker 1: to two metal plates creates a positively charged surface on
Speaker 1: one 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: Because 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. Jaeger 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 Jaeger would say, oh, there's poison gas here.
Speaker 1: So he started testing it, except it didn't work. The
Speaker 1: poison gas did not set off the detector, and as
Speaker 1: the story goes Yaeger 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: detector's 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 Maley 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 light bulb.
Speaker 1: You've got 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 tube's 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 tungsten filament inside, and
Speaker 1: then you get your stream. 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 electrons. 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'll cause a discharge
Speaker 1: between the two and the gas will act as a
Speaker 1: carrier for that electrical current. So a neon light is
Speaker 1: an implementation of the cold cathode tube technology. Melee's objective
Speaker 1: was to boost the signal from the detection circuit so
Speaker 1: that the signal could be strong enough to trigger an alarm,
Speaker 1: So not just that it would detect a drop in
Speaker 1: current or a change in the electrical current across these
Speaker 1: two plates, but that it would also have a strong
Speaker 1: enough signal so it could power a loud 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 a loud speaker and thus alerting you that there
Speaker 1: is in fact smoke in the area. Now, Jaeger, being
Speaker 1: an enterprising sort, partnered with Melee to launch a business
Speaker 1: offering smoke detectors in the late nineteen forties. However, these
Speaker 1: detectors weren't terribly practical because they required that high voltage
Speaker 1: to operate 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 first,
Speaker 1: nineteen f eight, at the Roman Catholic school in Chicago
Speaker 1: called Our Lady of the Angels School. Now, the origins
Speaker 1: of the fire have never been verified. No one knows
Speaker 1: exactly what started it, but it appeared to begin in
Speaker 1: the stairwell for the school, and the school had limited
Speaker 1: fire prevention measures in place. The school itself was an
Speaker 1: older building in Chicago and had been grandfathered into Chicago's
Speaker 1: safety standards because it had previously met earlier regulations. So
Speaker 1: when the city updated its fire safety regulations, one of
Speaker 1: the policies there was that older buildings that had passed
Speaker 1: the previous ones were considered safe. Students and staff were
Speaker 1: unaware of the danger of the fire until it became
Speaker 1: a critical threat, and more than ninety children died in
Speaker 1: that tragedy. It was a truly horrifying event and it
Speaker 1: illustrated the need to develop better fire detection and prevention methods.
Speaker 1: Research in Canada and the United States began looking into
Speaker 1: various catastrophic fires that had happened over the years, and
Speaker 1: according to doctor Jim Milk of the University of Maryland,
Speaker 1: these studies found evidence suggesting that had smoke detectors been
Speaker 1: available at the time, there would have been forty percent
Speaker 1: fewer deaths in those catastrophic fires. There were more than
Speaker 1: three hundred of them that they were looking at, and
Speaker 1: rise of heat detectors, which I'll talk about in a second,
Speaker 1: would have decreased the number of fatalities less than ten percent.
Speaker 1: And these were hypotheses, mind you, there was no way
Speaker 1: of knowing that that in fact would actually have been
Speaker 1: the 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 monitor increases in temperature and
Speaker 1: 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: It 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. See back in nineteen forty four,
Speaker 1: there was a guy named Glenn Seborg who had been
Speaker 1: asked to join the highly classified Manhattan Project. Now, this was,
Speaker 1: of course, the United States's 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. Seborg 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 and created numerous radioactive elements in the process.
Speaker 1: Elements that are above ninety two on the elemental table
Speaker 1: were all synthetic. They were all created in labs and
Speaker 1: their very unstable atoms. Now, among the ones that they
Speaker 1: worked on was one called amerasrium. So ameraserium is a
Speaker 1: synthetic element that was produced in the lab in a
Speaker 1: cyclotron experiment in Berkeley, California. The specific variant that we're
Speaker 1: interested in for this podcast is an isotope of amerasyrium.
Speaker 1: It's ameraserrium two forty one. And you know I mentioned
Speaker 1: what ions are, but what is an isotope case it's
Speaker 1: been a while since you've had basic science because I
Speaker 1: always have to look these up. I'm not trying to
Speaker 1: shame anybody. I get my stuff mixed up, so I
Speaker 1: got to look it up. Well. You know, an ion
Speaker 1: is an atom or molecule that has a net electric charge, right.
Speaker 1: That means it either has too many or too few
Speaker 1: electro electrons for it to balance out with the protons.
Speaker 1: That's an ion. Isotopes are different. You have the right
Speaker 1: number of protons and electrons, but you have different numbers
Speaker 1: of neutrons between two different two or more different variants
Speaker 1: of the same element. So ameraserrium two forty one and
Speaker 1: a marasyrium two forty two are nearly identical. They have
Speaker 1: the same number of protons and the same number of electrons,
Speaker 1: but ameraserrium two forty two has one neutron more than
Speaker 1: a maraserrium two forty one. It changes the atomic mass
Speaker 1: of that particular atom, but otherwise as the same protons
Speaker 1: and electrons as the other isotopes of that element. So
Speaker 1: the maracerrium two forty one is radioactive, which means it
Speaker 1: decays and gives off radiation. It's ionic radiation, so that
Speaker 1: means that the energy that's given off, the radiation that's
Speaker 1: given off is energetic enough to strip electrons off of
Speaker 1: atoms or molecules and ionizing them. A small amount of
Speaker 1: a maraserrium two forty one will ionize atoms like oxygen
Speaker 1: 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 thousandth 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 maraserium as a replacement
Speaker 1: for a high voltage circuit. That would take some time
Speaker 1: and a lot of study before determining that a maraserrium
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 nucleus. The nucleus of a helium atom includes
Speaker 1: two protons and two neutrons. That's an alpha particle two
Speaker 1: protons and two neutrons. An alpha particle has good ionization power,
Speaker 1: but it also doesn't have a lot of penetrative power.
Speaker 1: It can't go through matter very easily. It's a massive
Speaker 1: particle in the grand scheme of things and moves more
Speaker 1: slowly than other types of radiation, so an alpha particle
Speaker 1: is too weak to pass through a thin sheet of paper.
Speaker 1: It can only go through a few centimeters of air
Speaker 1: before it loses energy and can't move anymore. So while
Speaker 1: ameras serium two forty one is radioactive, it's considered relatively
Speaker 1: safe in small amounts and if kept in isolation. You
Speaker 1: wouldn't want to come into direct contact with the stuff,
Speaker 1: and you definitely wouldn't want to inhale or ingest any
Speaker 1: mrror serium or get it in an open wound because
Speaker 1: it is carcinogenic. But it would have to get past barriers.
Speaker 1: It's not even strong enough to get through the skin,
Speaker 1: but it is strong enough if you were to ingest
Speaker 1: it or breathe in some dust, it could potentially cause cancer.
Speaker 1: It could certainly increase your risk of developing cancer, so
Speaker 1: there is a danger to it. So your typical smoke
Speaker 1: detector actually has some radioactive material in it to create
Speaker 1: the ions that flow between two charged plates. The ions
Speaker 1: behave just as the ones did with Jaeger's high voltage device.
Speaker 1: It's the same sort of stuff. It's charged particles, So
Speaker 1: smoke particles will still interact with them, just as they
Speaker 1: would with Jaeger's invention with the high voltage grid, and
Speaker 1: they will still bind and cause a drop in current,
Speaker 1: and that's what triggers the circuit that powers the actual alarm.
Speaker 1: It would be nearly two decades between the invention of
Speaker 1: a maraserium to forty one and its application as an
Speaker 1: ion generator in a smoke detector. The United States Atomic
Speaker 1: Energy Commission would grant a license in nineteen sixty three
Speaker 1: authorizing the use of a maraserium to forty one in
Speaker 1: smoke detectors. And the thought was that the amount of
Speaker 1: radioactive material would be so tiny that it would not
Speaker 1: really stand to be a hazard, and it was just
Speaker 1: a very low risk, but there was a very real
Speaker 1: risk of fire and smoke, and so when you weigh
Speaker 1: it against each other and said, the risk of fire
Speaker 1: is high, and the risk of something happening because of
Speaker 1: this very tiny amount of radioactive material is low. It
Speaker 1: makes way more sense to err on the side of
Speaker 1: detecting fires. So two years later, in nineteen sixty five,
Speaker 1: a guy named Dwayne D. Persall introduced a battery powered
Speaker 1: smoke detector. This eliminated the need for that high voltage circuit,
Speaker 1: and Percell came by this accidentally. A lot of inventions
Speaker 1: really ended up being created as a consequence of some
Speaker 1: other unrelated effort. So in nineteen sixty three, that same
Speaker 1: year where the Atomic Energy Commission granted the license, Percell
Speaker 1: 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. Purcell 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 Persol Company and a
Speaker 1: spinoff company called Satratol or Sata Troll rather Sata Trill
Speaker 1: Corporation in Denver, Colorado. I find that name incredibly difficult
Speaker 1: to say properly. In fact, I'm sure I'm saying it incorrectly.
Speaker 1: But anyway, The company's main business was selling heating and
Speaker 1: air distribution equipment for commercial buildings, so sort of like
Speaker 1: an HVAC company for big, big, big buildings. But the
Speaker 1: product is engineered were working on was what he called
Speaker 1: a static neutralizer. The idea was he was going to
Speaker 1: create an ion generator, and the idea was that these
Speaker 1: ions would neutralize static electricity build up on equipment, and
Speaker 1: that's something that could be a real issue for industrial
Speaker 1: operations and clean rooms and stuff. So you need to
Speaker 1: have a way to neutralize static build up or else
Speaker 1: you can have a discharge that could ruin tons of work. However,
Speaker 1: his team had encountered a problem. They saw that their
Speaker 1: ion generator was getting clogged up pretty quickly. The ions
Speaker 1: were attracting particles like dust and stuff, and as it
Speaker 1: was attracting dust, it was starting to make the entire
Speaker 1: device as a whole less effective. An engineer named Lyman
Speaker 1: Blackwell was running tests to see what could be done
Speaker 1: to keep the ion generation going. While testing the system,
Speaker 1: they noticed that the ion meter they were using to
Speaker 1: monitor performance would occasionally fluctuate, and one of the technicians
Speaker 1: running the equipment was a smoker. He was chained smoking
Speaker 1: during the whole testing process. Eventually they figured out that
Speaker 1: the meter was detecting fluctuations in the ion flow whenever
Speaker 1: smoke was getting pulled in through the fan on the
Speaker 1: generator and inserted into the ion stream. So essentially they
Speaker 1: were making the same discovery that Jaeger had made decades earlier.
Speaker 1: But the big difference was that Percell's ion generator didn't
Speaker 1: require that high voltage to run because it was depending
Speaker 1: on that small amount of amerserium two forty one. So
Speaker 1: he had the bright idea to take this unexpected result
Speaker 1: and turn it into an actual product. Two years later,
Speaker 1: he had the first battery operated, ionization based smoke detector.
Speaker 1: He called it the Smoke Guard seven hundred, but it
Speaker 1: wasn't quite ready for the home market yet because government
Speaker 1: regulations had not yet caught up to the technology. We're
Speaker 1: going to get into that as well, because, as it
Speaker 1: turns out, it's not enough just to make tech that works.
Speaker 1: You have to make tech that works within the boundaries
Speaker 1: of laws and regulations. Meanwhile, a pair of inventors named
Speaker 1: Donald Steel and Robert Emmerk came up with an alternative
Speaker 1: method for detecting smoke with a device and this approach
Speaker 1: wouldn't used ionized particles at all, so there's no need
Speaker 1: to create any sort of ionization chamber. Instead, Steel and
Speaker 1: Emark created a smoke detector that relied upon light and
Speaker 1: photo detectors. So photo detectors. Those are that's light sensors, right,
Speaker 1: so sensor that detects light. They are two basic categories
Speaker 1: of light sensors. The first type are sometimes called photovoltaics.
Speaker 1: These are devices that emit electrons when they're exposed to light,
Speaker 1: so solar panels are a type of photovoltaic cells. They
Speaker 1: generate electricity when exposed to light. The other type of
Speaker 1: light sensor would be the photo resistor or photoconductor. These
Speaker 1: sensors have electrical properties that change if they are actually
Speaker 1: exposed to light. So, for example, a photo resistor has
Speaker 1: a relatively high electrical resistance when it's in the dark,
Speaker 1: so that material resists the flow of electricity going through it. However,
Speaker 1: as the material is exposed to light, the electrical resistance
Speaker 1: decreases and electricity can pass through it more readily. So
Speaker 1: if you place one of these devices in a circuit
Speaker 1: and you have a voltage detector also attached to that circuit.
Speaker 1: The detector will pick up changes in voltage as light
Speaker 1: hits the sensor. Now, you could try and build a
Speaker 1: smoke detector that works by having a light shining on
Speaker 1: a photosensor 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 vents,
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 workaround to this. So instead of
Speaker 1: an alarm that goes off when a light no longer
Speaker 1: is shining on, it, design a 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 got a light
Speaker 1: at one end, and it's open so that air can
Speaker 1: come into the chamber at a nine degree angle, like
Speaker 1: a perpendicular angle to this light, and tucked away just
Speaker 1: a bit, you have a little alcove where there's a sensor.
Speaker 1: So under normal conditions, the light is going through the chamber,
Speaker 1: but the sensor is tucked in at a right angle,
Speaker 1: so it's not picking up any light. The sensor stays
Speaker 1: in the dark. However, if smoke enters the chamber that
Speaker 1: the light is passing through, some of that light hits
Speaker 1: the smoke and starts to scatter. And this is the
Speaker 1: same sort of effect you would see if you were
Speaker 1: driving a car on a really foggy day. It's why
Speaker 1: you're not supposed to use the high beams on your
Speaker 1: head lights when you're in the fog. The light will
Speaker 1: hit the fog and scatter, and it's more likely to
Speaker 1: make it harder for you to see rather than easier. Well,
Speaker 1: on 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 since they're trying to detect
Speaker 1: a dip in brightness. However, it's also not fool proof
Speaker 1: because vapor or dust could cause false alarms. Now, during
Speaker 1: all this innovation, changes were starting to happen on regulatory
Speaker 1: levels around the world, and when we come back, I'll
Speaker 1: talk more about how that played out in the United States.
Speaker 1: But first let's take another quick break. All right, So
Speaker 1: 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. If lives
Speaker 1: literally hang in the balance, it's important. So this is
Speaker 1: the same basic underlying philosophy we see in agencies that
Speaker 1: monitor stuff like food processing, pharmaceutical development and production. The
Speaker 1: era I'm talking about in the late nineteen sixties in
Speaker 1: the United States was a particularly tumultuous time. You had
Speaker 1: 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 intended that ignited civil unrest
Speaker 1: across the entire country, and in turn that was testing
Speaker 1: the limits of police forces and fire prevention and fire
Speaker 1: extinguishing services. So this prompted the US Congress to re
Speaker 1: examine policies around safety to better protect citizens. One thing
Speaker 1: to come out of this was the Fire Research and
Speaker 1: Safety Act, which was signed into law by then President
Speaker 1: Lyndon Johnson. The President was citing some figures that suggested
Speaker 1: as many as twelve thousand Americans had died in fires
Speaker 1: in nineteen sixty. Later estimates adjusted that number down significantly
Speaker 1: to like eight thousand, but that's still way too many people.
Speaker 1: The Act called for the creation of a twenty person
Speaker 1: panel to study the challenges and make recommendations for new
Speaker 1: safety standards that could be carried out at the federal
Speaker 1: level and require any building in the US to follow
Speaker 1: certain processes to make sure that they were safe for people,
Speaker 1: and it took a few years for all of this
Speaker 1: to actually coalesce into a report. I mean, it was
Speaker 1: a big task, and we also happen to know that
Speaker 1: things in the US government don't go super fast. But
Speaker 1: in nineteen seventy three, the panel released a report. The
Speaker 1: report was titled America Burning, which is pretty sobering all
Speaker 1: on its own. And America was leading the way in
Speaker 1: industrial nations when it came to per capita deaths and
Speaker 1: property loss due to fire. So the argument they were
Speaker 1: making was that America is this incredibly advanced country, Why
Speaker 1: the heck are we losing so much to fire? We
Speaker 1: should be doing better than that, And eighty percent of
Speaker 1: the deaths were occurring in people's homes. The report also
Speaker 1: contained pictures of Percell's smoke Guard detector. He had come
Speaker 1: to overcome challenges to make his detectors practical and safe. Now.
Speaker 1: His original design did not have a battery. Instead, it
Speaker 1: was to be hardwired into the electrical system of a building.
Speaker 1: It didn't require two hundred and twenty volts like the
Speaker 1: earlier smoke detectors off 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 one 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 supply of electricity anymore, and
Speaker 1: not the proper voltage anyway. And we're talking about something
Speaker 1: 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: Percell included a small card in the box for the
Speaker 1: smoke Guard seven hundred, and customers were meant to take
Speaker 1: the card and then fill out little forms on the
Speaker 1: card with their own information, including their address and the
Speaker 1: date that they installed their smoke detector, and Personal's company
Speaker 1: would 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 battery. And this was specifically in case someone might
Speaker 1: be out of town when the battery starts to give out.
Speaker 1: They wanted it to last long enough so that you
Speaker 1: would have time to get back and find out, oh, gosh,
Speaker 1: I need to switch out the batteries on my smoke detector.
Speaker 1: The government also had to balance out the cost of
Speaker 1: installing fire prevention systems and homes, including in newly constructed homes. Initially,
Speaker 1: plans called 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 weren't good enough to do that,
Speaker 1: and they were really expensive, and that smoke detectors were
Speaker 1: much better for the purpose of preventing fatalities. And so
Speaker 1: that meant that they got rid of the rise of
Speaker 1: heat detector requirement, and that helped bring the cost down
Speaker 1: of implementing fire protection systems and homes, and that in
Speaker 1: turn increased the likelihood that people would actually follow the
Speaker 1: rules and adopt smoke detectors. The regulations paved the way
Speaker 1: for Personal to manufacture, market, and sell his smoke detectors
Speaker 1: to the American public, who could be reassured that the
Speaker 1: devices would actually provide a valuable and potentially life saving service.
Speaker 1: He scaled up his company to meet demand before eventually
Speaker 1: selling it off in nineteen seventy seven. And from everything
Speaker 1: I've read about him, it sounds like he was motivated
Speaker 1: not only by an entrepreneurial spirit, although he certainly had that,
Speaker 1: but also a genuine desire to make his community and
Speaker 1: the world a better place if he could. And I
Speaker 1: think that's pretty cool. Since the introduction of the optical
Speaker 1: and the ionization chamber based smoke detectors, we've seen some innovations,
Speaker 1: but the basic principles all remain the same. There are
Speaker 1: smoke detectors that incorporate both types of methodologies, meaning there
Speaker 1: are smoke detectors that have independent systems to detect the
Speaker 1: presence of smoke, and we've seen some incorporate other types
Speaker 1: of tech, such as network connectivity in the form of
Speaker 1: products like the Nest Protect smoke detector, and those smoke
Speaker 1: detectors add a little more functionality to the basic kind.
Speaker 1: They work on basically the same principle, but they have
Speaker 1: some more features. For example, they can send information across
Speaker 1: a local area network wirelessly and then that network can
Speaker 1: send an alert to you on an app on a smartphone,
Speaker 1: and that could be valuable if, for example, you're away
Speaker 1: from your home when an alarm goes off. To give
Speaker 1: you a notification, you can perhaps either call home, or
Speaker 1: if no one's home, you might even call a fire
Speaker 1: department to go and check on your home to make
Speaker 1: sure that everything is all right. And most homes have
Speaker 1: multiple smoke detectors. In fact, you're supposed to have one
Speaker 1: outside of every bedroom, for example, as well as maybe
Speaker 1: one in the kitchen. My own home has six of
Speaker 1: the darn things, and it can be an issue of
Speaker 1: figuring out which detector is going off, and that could
Speaker 1: be of vital importance. So with connected detectors, then you
Speaker 1: get a notification saying toctor number three is going off,
Speaker 1: and you know that number three happens to be outside
Speaker 1: the guest room, so you would be able to very
Speaker 1: quickly figure out what's going on, as opposed to trying
Speaker 1: to determine which of your numerous alarms is going off.
Speaker 1: It also means that if a battery is running out
Speaker 1: and a smoke detector is chirping, or maybe a battery
Speaker 1: was just a bad battery and starts to chirp, you
Speaker 1: can more quickly track down which detector is making the
Speaker 1: chirping noise. This really applies to folks like me because
Speaker 1: I live in a townhouse that has a few floors,
Speaker 1: and the center of the townhouse is essentially like a chimney.
Speaker 1: There are stairs that go from the bottom floor, and
Speaker 1: the stairwells open all the way to the top of
Speaker 1: the townhouse, so it's like an echo chamber inside my house,
Speaker 1: which means when something like a smoke detector starts to chirp,
Speaker 1: I can't easily identify whether it's on the floor I'm
Speaker 1: on the floor above me or the floor below me.
Speaker 1: And I have six smoke detectors. If it's time to
Speaker 1: replace the batteries, that's one thing, But if it's just
Speaker 1: that a battery is going bad early, then I have
Speaker 1: to figure out which of those detectors is making the problem.
Speaker 1: And exacerbating this issue for me is the fact that
Speaker 1: I have a cute little doggie named tibult and the
Speaker 1: chirping smoke detector noise causes him intense distress, like he
Speaker 1: starts to shake with fear. So I get really upset
Speaker 1: when one of my smoke detectors starts to chirp prematurely.
Speaker 1: There's no smoke or anything. It's just giving me a
Speaker 1: chirp alarm. But that's a me problem. One other thing
Speaker 1: that a lot of smoke detectors can do these days
Speaker 1: is they can also perform as carbon monoxide detectors. So
Speaker 1: carbon monoxide is an odorless and colorless gas, so human
Speaker 1: beings can't easily detect it, and it's also toxic. It's
Speaker 1: a byproduct from burning carbon based fuels like gasoline, heating oil,
Speaker 1: or natural gas, and in confined spaces it can be
Speaker 1: really dangerous stuff, so like a garage, for example. And
Speaker 1: while we humans can't really detect carbon monoxide with our
Speaker 1: own senses, there are a lot of other ways to
Speaker 1: see if the stuff is around. So carbon monoxide detectors
Speaker 1: can work using one of a few different methods. Upon detection,
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, and one
Speaker 1: you might have what are called biomimetic sensors. These sensors
Speaker 1: mimic us the name some sort of biological function, such
Speaker 1: as hemoglobin, which interacts with carbon monoxide. So these sensors
Speaker 1: have a gel inside of them, and that gel can
Speaker 1: absorb carbon monoxide. As the gel does absorb carbon monoxide,
Speaker 1: the gel changes color. Separate sensor that's monitoring the color
Speaker 1: of the gel, and if the gel changes, then the
Speaker 1: sensor picks up on that change and sends a signal
Speaker 1: to the alarm. These sensors can actually be reset. The
Speaker 1: gel will return to its original color once it gets
Speaker 1: rid of that carbon monoxide, but it has to be
Speaker 1: set in an environment that's free of carbon monoxide for
Speaker 1: several hours in order to reset. The next type is
Speaker 1: the metal oxide semiconductor sensor. This has components that have
Speaker 1: a certain level of electrical resistance, very much like the
Speaker 1: optical smoke detectors I talked about earlier. So these components
Speaker 1: react with carbon monoxide in a way that lowers the
Speaker 1: material's electrical resistance and so meters are monitoring a voltage
Speaker 1: across a circuit, and if it detects this change in voltage,
Speaker 1: then it will send a signal to the alarm. And
Speaker 1: the third type of sensor that you could find in
Speaker 1: a carbon monoxide detector as an electrochemical sensor. These sensors
Speaker 1: also detect changes an electrical current in the presence of
Speaker 1: carbon monoxide, but they have electrodes that are inside a
Speaker 1: chemical solution, so they're actually engulfed in a chemical solution.
Speaker 1: Around these electrodes and the chemicals in the solution react
Speaker 1: very very quickly in the presence of carbon monoxide, and
Speaker 1: that changes the electrical qualities of the solution, which means
Speaker 1: that you are able to detect a change in the
Speaker 1: circuit very very quickly. In fact, this stuff is used
Speaker 1: in professional settings. It's a very sensitive kind of alarm. Today,
Speaker 1: there are a lots of smoke detectors that double as
Speaker 1: carbon monoxide detectors with separate components monitoring the environment. I
Speaker 1: hope you enjoyed that episode from February tenth, twenty twenty,
Speaker 1: how smoke detectors work. As a reminder, I will be
Speaker 1: back next week with all new episodes. I have no
Speaker 1: idea what they'll be about because currently I'm on space
Speaker 1: mountain or something. I hope you're all well, and I'll
Speaker 1: talk to you again really soon. Tech Stuff is a
Speaker 1: production of iHeartRadio's House Stuff Works. For more podcasts from iHeartRadio,
Speaker 1: visit the iHeartRadio app, Apple Podcasts, or wherever you listen
Speaker 1: to your favorite shows.