WEBVTT Kind: captions Language: en 00:00:00.000 --> 00:00:01.840 Before we get started I want to let you know that   00:00:01.840 --> 00:00:05.360 I will not be setting any of the alarms off in this video. 00:00:06.080 --> 00:00:08.492 When you last went shopping for smoke detectors, 00:00:08.799 --> 00:00:13.971 did you notice that there were two different detection technologies available to put your dollars towards? 00:00:13.971 --> 00:00:17.966 Let me tell ya, even though I shop for smoke alarms every other Wednesday 00:00:17.966 --> 00:00:19.296 it hadn’t occurred to me. 00:00:20.141 --> 00:00:23.138 That’s a lie, this is just a silly setup. 00:00:23.138 --> 00:00:26.499 In fact I only rarely go shopping for smoke detectors, 00:00:26.499 --> 00:00:29.905 but the last time I did was to replace one of mine because 00:00:29.905 --> 00:00:32.000 SOMEbody had installed the wrong type! 00:00:32.800 --> 00:00:34.537 The wrong type? 00:00:34.537 --> 00:00:37.172 There’s a wrong type of smoke detector? 00:00:38.017 --> 00:00:41.363 Well… suboptimal might be a better word. 00:00:41.363 --> 00:00:45.725 See, the detector outside my  bedroom is in a hallway that leads to the kitchen. 00:00:45.725 --> 00:00:50.011 And it’s right next to a return vent for the  building’s HVAC system. 00:00:50.011 --> 00:00:56.919 That’s not ideal from the start but it’s hardwired and interconnected to the other alarms here so moving it isn’t an option. 00:00:56.919 --> 00:01:02.321 Anyway, being almost in the kitchen and having  kitchen air pulled near to it, 00:01:02.321 --> 00:01:06.419 I was getting nuisance alarms every time I made toast. 00:01:06.419 --> 00:01:07.982 And I am not exaggerating. 00:01:07.982 --> 00:01:08.791 Every. 00:01:08.791 --> 00:01:09.710 Single. 00:01:09.710 --> 00:01:10.210 Time. 00:01:10.560 --> 00:01:13.831 And often when I dared to simply use the oven! 00:01:13.831 --> 00:01:16.606 Didn’t even matter if I had put something in it yet. 00:01:16.606 --> 00:01:17.975 What was going on? 00:01:17.975 --> 00:01:19.791 Well, that smoke alarm 00:01:19.791 --> 00:01:21.392 (which is now right here) 00:01:21.392 --> 00:01:26.555 used the good old fashioned ionization chamber for its smoke  detection abilities. 00:01:26.555 --> 00:01:28.496 It’s slightly radioactive! 00:01:29.120 --> 00:01:32.160 Now that’s a tried and true method for detecting smoke, 00:01:32.160 --> 00:01:35.622 in fact in some cases it works a little too well, 00:01:35.622 --> 00:01:42.088 uh but these days it’s revealing its weaknesses and according to some these should be considered obsolete. 00:01:42.088 --> 00:01:48.000 I replaced it with a photoelectric smoke detector and  not only have the nuisance alarms completely stopped 00:01:48.000 --> 00:01:52.988 but I will probably have more advanced warning of a fire should one happen. 00:01:52.988 --> 00:01:55.847 At least, depending on the fire. 00:01:56.160 --> 00:01:58.327 Ah! A nuanced discussion! 00:01:58.327 --> 00:02:01.071 Those go great with the internet. 00:02:01.071 --> 00:02:06.407 Let me start out by saying that regardless of what smoke alarms you might have in your home 00:02:06.407 --> 00:02:12.119 the most important thing is that you have them and that you know they are functional. 00:02:12.119 --> 00:02:15.469 If you can’t remember the last time you checked your smoke alarms, 00:02:15.469 --> 00:02:17.155 do it right now. 00:02:17.155 --> 00:02:20.900 Seriously, pause the video, make sure you have them, 00:02:20.900 --> 00:02:26.072 and if you’re able to test them without setting  off a central monitoring system, do it. 00:02:26.072 --> 00:02:32.857 Most every fire-related tragedy we hear about these days  stems from a home without working smoke alarms, 00:02:32.857 --> 00:02:37.636 meaning those tragedies were almost certainly preventable, and all too easily. 00:02:37.636 --> 00:02:40.372 You should have a smoke alarm in every bedroom, 00:02:40.372 --> 00:02:44.492 in locations immediately outside of sleeping areas such as hallways, 00:02:44.492 --> 00:02:49.252 and in addition to that there should be  at least one on every level of your home. 00:02:49.252 --> 00:02:54.000 Consult your local fire authority for more specific  recommendations and requirements in your area. 00:02:54.800 --> 00:02:57.006 Let’s start with a bit of history. 00:02:57.006 --> 00:02:59.780 Smoke detectors are a fairly recent invention 00:02:59.780 --> 00:03:04.240 and the household smoke alarm didn’t hit meaningful mass production until the 1970’s. 00:03:04.800 --> 00:03:09.132 We needed to clear two hurdles before the smoke  alarm would be commonplace: 00:03:09.132 --> 00:03:14.179 First, a reliable and relatively cheap smoke sensor needed to be devised. 00:03:14.179 --> 00:03:19.701 And secondly, we’d need to figure out how to make some cheap and mass-producible electronics 00:03:19.701 --> 00:03:24.319 which could monitor that sensor and sound an alarm if smoke was detected. 00:03:24.319 --> 00:03:30.984 As it happens, the principle on which these first smoke sensors operate was discovered by accident in the 1930’s 00:03:30.984 --> 00:03:33.527 by Swiss physicist Walter Jaeger. 00:03:33.527 --> 00:03:39.695 He was trying to invent something which could detect  poison gas, which didn’t work. 00:03:39.695 --> 00:03:45.758 But his device did react to the smoke particles coming from his lit frustration cigarette. 00:03:45.758 --> 00:03:47.440 Or so goes the story. 00:03:48.080 --> 00:03:53.591 The sensor used in the first commercial smoke alarms — and plenty that are still produced today — 00:03:53.591 --> 00:03:57.781 operates on the same principle as Jaeger’s experimental device. 00:03:57.781 --> 00:04:01.031 It is made of a pair of electrodes that span an air gap, 00:04:01.031 --> 00:04:07.188 and sitting below a hole in one of the electrodes is a teensy little bit of americium-241 00:04:07.188 --> 00:04:10.480 which emits alpha particles by way of being, ya know, 00:04:10.480 --> 00:04:11.970 radioactive. 00:04:11.970 --> 00:04:15.583 As the americium decays and flings out those particles, 00:04:15.583 --> 00:04:19.748 they collide with the nitrogen and oxygen  atoms that make up the bulk of air 00:04:19.748 --> 00:04:22.687 and knock loose some of their electrons. 00:04:22.687 --> 00:04:26.810 This results in some charged gas molecules between the two plates. 00:04:26.810 --> 00:04:33.177 And with the help of a power source to maintain a voltage potential between the plates, often a 9-volt battery, 00:04:33.177 --> 00:04:37.105 those now charged molecules become attracted to the electrodes, 00:04:37.105 --> 00:04:41.918 and the end result once they move towards them is a lil’ bit of current flow. 00:04:41.918 --> 00:04:46.310 And I do mean a lil’ bit, about 100 picoamps. 00:04:46.720 --> 00:04:51.120 However, when something’s burning and  releasing smoke particles into the air,   00:04:51.680 --> 00:04:54.907 once those smoke particles get between the two electrodes, 00:04:54.907 --> 00:05:00.238 they start absorbing or blocking the alpha particles coming from the americium. 00:05:00.238 --> 00:05:04.240 That prevents the ionization of the nitrogen and oxygen molecules, 00:05:04.240 --> 00:05:07.547 which stops the flow of current between the plates. 00:05:07.547 --> 00:05:13.746 A relatively simple electronic circuit can monitor for current flow and sound an alarm if it stops, 00:05:13.746 --> 00:05:18.014 and with the development of the MOSFET and its cheapening in the 1970’s, 00:05:18.014 --> 00:05:23.840 suddenly we had everything we needed to produce an inexpensive, automatic device for warning of the presence of smoke. 00:05:24.720 --> 00:05:31.576 Now, if you’re anything like me, you might think  that resorting to radioactive isotopes seems... 00:05:31.576 --> 00:05:33.278 a bit much. 00:05:33.278 --> 00:05:37.327 It’s not dangerous or anything,  alpha particles are easily stopped - 00:05:37.327 --> 00:05:41.156 the radiation can’t even get through the plastic shell of the alarm. 00:05:41.156 --> 00:05:44.800 But, it still feels like a rather… 00:05:44.800 --> 00:05:46.638 exotic technique. 00:05:46.638 --> 00:05:50.677 After all, we can see smoke particles with our eyes. 00:05:50.677 --> 00:05:52.926 And our eyes work because of light. 00:05:52.926 --> 00:05:56.686 And since we can see smoke using our light-sensing eyes, 00:05:56.686 --> 00:06:01.336 there’s probably a way to use a light sensor to detect smoke. 00:06:01.336 --> 00:06:02.537 Indeed there is. 00:06:02.537 --> 00:06:10.053 All the way back in 1972, Donald F. Steele and Robert B. Enemark devised an optical smoke detector, 00:06:10.053 --> 00:06:15.610 which worked using essentially the same principle  as modern-day photoelectric smoke detectors. 00:06:16.000 --> 00:06:21.840 Their idea was to put a light source and two  light sensing photocells in a detection chamber   00:06:21.840 --> 00:06:26.800 which would allow air to freely move through  it, but which contained a series of light traps   00:06:26.800 --> 00:06:29.597 to prevent ambient light from getting in. 00:06:29.597 --> 00:06:36.161 FYI, photocells weren’t by any means a new thing at this point - this wasn’t groundbreaking tech, 00:06:36.161 --> 00:06:37.833 just a clever idea. 00:06:37.833 --> 00:06:43.144 Anyway, the sensors were arranged so that only one of them could “see” the light source. 00:06:43.144 --> 00:06:49.363 The second sensor had no line of sight to the light source, with a series of light-blocking vanes in the way. 00:06:49.363 --> 00:06:51.992 When smoke particles entered the chamber, though, 00:06:51.992 --> 00:06:57.877 light from the light source would reflect off those particles in every which way and become scattered. 00:06:57.877 --> 00:07:00.901 Think of it like a laser beam in a smoky room. 00:07:00.901 --> 00:07:04.633 The second sensor could now “see” the light coming from the light source, 00:07:04.633 --> 00:07:07.840 thus smoke was detected, and an alarm is sounded. 00:07:08.560 --> 00:07:15.659 These early photoelectric alarms used two sensors  as a means of testing the functionality of the light source. 00:07:15.659 --> 00:07:21.593 If no light was detected in the first sensor,  this would indicate that the light source had failed. 00:07:21.593 --> 00:07:26.128 Which was pretty likely as the early designs used incandescent lamps. 00:07:26.128 --> 00:07:27.120 And no, 00:07:27.120 --> 00:07:33.549 they were not battery-powered, which is likely a reason  the ionization sensor was preferred for so long.   00:07:34.000 --> 00:07:39.027 These days, though, a much simpler and way less  power-hungry arrangement 00:07:39.027 --> 00:07:43.546 of infrared LED and single photodetector is used. 00:07:43.546 --> 00:07:48.656 The photodetector is positioned in the detection chamber so that it can’t see the LED, 00:07:48.656 --> 00:07:52.635 and every few seconds the detector will put out a little  blip of light. 00:07:52.635 --> 00:07:59.416 It may also blip a visible LED on the exterior to give indication that it’s powered on and functional. 00:07:59.416 --> 00:08:04.541 If it can't see the blip in the photodetector, then the air must be clean. 00:08:04.541 --> 00:08:11.840 If, however, the chamber has smoke in it, the smoke particles will scatter the light and some will be picked up by the photodetector. 00:08:12.480 --> 00:08:15.231 That usually won’t trigger an alarm right away, though. 00:08:15.231 --> 00:08:22.080 Modern designs are often programmed upon first detection to begin an additional and more frequent series of blips 00:08:22.080 --> 00:08:24.269 to guard against false alarms. 00:08:24.269 --> 00:08:27.840 If, for instance, a piece of dust happened to float into the chamber, 00:08:28.400 --> 00:08:31.891 well you wouldn’t want the alarm to go off just for that.   00:08:31.891 --> 00:08:39.054 So it will perform a routine where it checks a  few more times in rapid succession for scattered light. 00:08:39.054 --> 00:08:46.517 It may also be looking for an increasing signal amplitude and thus thicker smoke over time before committing to an alarm condition, 00:08:46.517 --> 00:08:49.050 though that’s speculation on my part. 00:08:49.050 --> 00:08:53.908 In any case, if it keeps seeing light hit the photocell after  a pre-programmed test period, 00:08:53.908 --> 00:08:55.767 it will sound the alarm. 00:08:56.160 --> 00:09:02.000 So, we have two commonly-produced and easily  obtainable smoke detection technologies at hand:   00:09:02.560 --> 00:09:08.000 one using commodity LEDs, photodetectors,  a bit of electronics and some plastic,   00:09:08.000 --> 00:09:12.961 and the other using some  plastic, a bit of electronics, a couple of metal plates, and 00:09:12.961 --> 00:09:16.167 an exotic synthetic radioisotope of americium. 00:09:18.000 --> 00:09:20.212 Why are we still making this second kin- 00:09:20.212 --> 00:09:21.252 [exasperation noises] 00:09:21.252 --> 00:09:24.868 That’s a good question, but before I move on to the pros and cons here, 00:09:24.868 --> 00:09:30.455 I want to share that the principle of optical smoke detection is as flexible as it is simple. 00:09:30.455 --> 00:09:33.720 While spot-sensing smoke alarms work as I’ve described, 00:09:33.720 --> 00:09:40.550 another option is to shine a beam of light across a large distance and measure its received intensity. 00:09:40.550 --> 00:09:45.963 You can modulate that beam in some way to allow a sensor to pick up a signal through ambient light, 00:09:45.963 --> 00:09:51.920 and a sudden dropout of that modulated signal or  simple intensity loss can indicate smoke. 00:09:52.880 --> 00:09:57.339 These are often used in buildings with large open spaces like atria, 00:09:57.339 --> 00:10:03.128 and in such buildings you might have seen a funny-looking device at one end of a ceiling pointing across the building 00:10:03.128 --> 00:10:06.661 to another one on the other end, or perhaps a retroreflector. 00:10:06.661 --> 00:10:13.264 There’s a pretty good chance that was, in fact, a smoke sensor incorporated into the building’s fire alarm system. 00:10:13.520 --> 00:10:16.617 Alright, with two very different detection methods, 00:10:16.617 --> 00:10:22.541 it’s probably no surprise that the two technologies respond  differently to different kinds of smoke.   00:10:23.120 --> 00:10:28.158 This may in part explain why ionization alarms are still on the market - 00:10:28.158 --> 00:10:32.831 remember how this one was sensing smoke whenever I made toast? 00:10:32.831 --> 00:10:36.365 Toastmaking is really just slightly burning bread, 00:10:36.365 --> 00:10:43.482 and even though I don’t like my toast all that dark, little  whisps of smoke are produced as the surface of the bread gets singed. 00:10:43.482 --> 00:10:47.237 These smoke particles are really, really small though. 00:10:47.237 --> 00:10:50.292 So small that they can barely be seen. 00:10:50.292 --> 00:10:56.429 However, those particles are very good at absorbing the alpha particles emitted from the americium, 00:10:56.429 --> 00:11:01.741 and so not a lot of that kind of smoke is needed to set off one of these alarms. 00:11:02.000 --> 00:11:05.296 These very small, often invisible smoke particles 00:11:05.296 --> 00:11:08.731 are commonly emitted from things that are actively on fire. 00:11:08.731 --> 00:11:15.256 And this makes the ionization alarm technology particularly sensitive to the flaming stage of a fire. 00:11:15.256 --> 00:11:21.607 In fact, even apparently clean-burning flames can set them off - that may have been why just using the oven 00:11:21.607 --> 00:11:23.600 was prone to causing an alarm in my case. 00:11:24.320 --> 00:11:27.017 Car exhaust can also trigger these alarms, 00:11:27.017 --> 00:11:30.925 which is why smoke alarms are rarely recommended in garages. 00:11:30.925 --> 00:11:34.842 This has been a particularly puzzling  thing to me as, ya know, 00:11:34.842 --> 00:11:42.141 cars catch on fire sometimes and I would think a smoke alarm in the place where you keep your car is a decent idea. 00:11:42.141 --> 00:11:49.754 Anyway, while ionization alarms are really good — arguably too good — at detecting fine smoke particles, 00:11:49.754 --> 00:11:55.218 they are absolutely crap at detecting large smoke particles. 00:11:55.218 --> 00:12:01.963 If a room is slowly filling up with visible smoke, an ionization alarm may very well do nothing. 00:12:02.936 --> 00:12:07.741 You might think, "oh, so what? You said it’s good at detecting smoke from a flaming fire, 00:12:07.741 --> 00:12:11.440 and so long as it’s gonna wake me when a fire’s  actually happening what does it matter?" 00:12:12.400 --> 00:12:16.566 Well, most fires don’t just suddenly happen. 00:12:16.566 --> 00:12:18.018 They start slowly. 00:12:18.018 --> 00:12:21.351 And in the initial smoldering stages of a fire, 00:12:21.351 --> 00:12:25.222 the smoke particles tend to be the large, visible kind. 00:12:25.222 --> 00:12:31.716 If all you have in your home are ionization alarms, they may not react at all to that situation. 00:12:32.485 --> 00:12:33.841 And that’s bad! 00:12:34.080 --> 00:12:38.449 Studies comparing ionization and photoelectric  smoke sensing technologies 00:12:38.449 --> 00:12:42.229 have routinely shown that in the smoldering stage of a fire, 00:12:42.229 --> 00:12:48.022 photoelectric alarms respond much more quickly than their ionization counterparts. 00:12:48.022 --> 00:12:52.825 Some experiments have shown photoelectric alarms responding to the early stages of fire 00:12:52.825 --> 00:12:56.727 more than an hour before an ionization alarm does. 00:12:57.120 --> 00:13:00.486 Early warning of such fires is obviously valuable, 00:13:00.486 --> 00:13:07.558 and may give occupants time to find the source of the smoke and prevent  a destructive flaming fire altogether. 00:13:07.920 --> 00:13:11.920 And let’s not forget that smoke itself is very dangerous, 00:13:11.920 --> 00:13:15.760 with many fire-related fatalities happening due to smoke inhalation.   00:13:16.640 --> 00:13:21.036 In an Australian 60 minutes program which aired  back in 2014, 00:13:21.036 --> 00:13:25.919 a photoelectric alarm was activated about seven minutes into a simulated fire, 00:13:25.919 --> 00:13:33.343 meanwhile three ionization alarms didn’t respond at all to the very smoky test environment. 00:13:33.343 --> 00:13:35.108 Which is astounding! 00:13:35.108 --> 00:13:42.467 A smoke alarm which doesn’t react to a smoldering fire and a smoke-filled room isn’t a very useful smoke alarm. 00:13:43.120 --> 00:13:46.123 Some jurisdictions have reacted to this new knowledge 00:13:46.123 --> 00:13:52.837 by mandating photoelectric alarm technology and discouraging the use of ionization detectors. 00:13:52.837 --> 00:13:55.898 However, not all of them have. 00:13:55.898 --> 00:14:00.068 Ionization alarms still have that one narrow advantage; 00:14:00.068 --> 00:14:03.436 they do react more quickly to a flaming fire, 00:14:03.436 --> 00:14:07.849 and a photoelectric alarm needs  large-ish particles which can be seen, 00:14:07.849 --> 00:14:11.981 so fires which develop suddenly may not trigger them right away. 00:14:11.981 --> 00:14:14.157 Because of this situational difference, 00:14:14.160 --> 00:14:17.998 here in the US neither the The National Fire Prevention Association 00:14:17.998 --> 00:14:23.956 nor the United States Fire Administration take a firm position on the two technologies. 00:14:23.956 --> 00:14:29.034 They recognize the pros and cons but say that, since all fires are different, 00:14:29.034 --> 00:14:32.080 making a recommendation either way doesn’t make sense. 00:14:32.960 --> 00:14:35.112 And I sorta get that. 00:14:35.112 --> 00:14:38.160 If an ionization alarm is better in some fires, 00:14:38.800 --> 00:14:41.339 well then maybe it’s good to have them. 00:14:41.339 --> 00:14:46.955 But there are several problems with fixating on that situational speed benefit. 00:14:46.955 --> 00:14:54.715 The first is that fires which are suddenly flaming without having any smoldering action aren’t exactly common. 00:14:54.715 --> 00:15:01.200 It’s not like they never happen, one possible case might be if a cat knocks over a lit candle onto a tablecloth,   00:15:01.200 --> 00:15:06.321 but especially when people are sleeping, I don't think it's that common for a flaming fire 00:15:06.321 --> 00:15:07.928 to come out of nowhere. 00:15:07.928 --> 00:15:11.277 I spent some time looking for statistics and came up empty. 00:15:11.277 --> 00:15:14.720 If you know of a good source of  information regarding this please share it below. 00:15:15.440 --> 00:15:18.345 The second and perhaps most important issue here 00:15:18.345 --> 00:15:25.601 is that while ionization alarms are generally faster at detecting a flaming fire than their photoelectric counterparts… 00:15:26.472 --> 00:15:29.682 it’s a matter of seconds, and not minutes. 00:15:29.682 --> 00:15:35.360 When a house fire’s going on  it's not gonna be a nice clean burning fire for long at all, 00:15:35.360 --> 00:15:40.974 and smoke thick enough to trigger a  photoelectric alarm will accumulate pretty quickly. 00:15:40.974 --> 00:15:45.770 Surely there have been cases  in which the seconds mattered for survivability, 00:15:45.770 --> 00:15:53.840 but of course the counterargument is that a photoelectric alarm may have given you an hour’s advanced warning in a different situation. 00:15:53.840 --> 00:15:57.331 Now I can hear you asking; why not both? 00:15:57.331 --> 00:16:02.614 Smoke alarms are pretty cheap, so why not have both detection technologies? 00:16:02.614 --> 00:16:06.266 Well,  the smoke alarm manufacturers are way ahead of you 00:16:06.266 --> 00:16:09.441 offering dual-sensing alarms. 00:16:09.441 --> 00:16:11.712 There’s a problem with these, though. 00:16:12.000 --> 00:16:17.212 They aren’t exactly clear on how those sensors get used. 00:16:17.212 --> 00:16:23.432 The packaging of this one implies that it would sound the alarm if either sensor detects smoke, 00:16:23.432 --> 00:16:25.200 but the included user guide 00:16:25.760 --> 00:16:28.696 doesn’t clarify whether this is in fact the case. 00:16:28.696 --> 00:16:33.332 It simply says the alarm sounds when combustion products are detected. 00:16:33.332 --> 00:16:40.951 Some alarms like this may not go off unless both sensors agree that there is smoke - and in that case, 00:16:40.951 --> 00:16:47.624 you’re not actually getting any benefit at all as it will always be the slowest response between the two technologies. 00:16:47.624 --> 00:16:54.788 And the reason why they might be programmed this way has to do with the final major issue with ionization alarms; 00:16:54.788 --> 00:16:56.320 false alarms. 00:16:56.320 --> 00:17:01.853 A smoke alarm which goes off when it shouldn’t  is a nuisance that most of us have dealt with at some point. 00:17:01.853 --> 00:17:08.061 And ionization alarms, thanks to their hyper-sensitivity towards certain kinds of invisible smoke particles, 00:17:08.061 --> 00:17:12.400 are particularly prone to false triggers - especially when placed near kitchens. 00:17:13.280 --> 00:17:17.982 False alarms aren’t just annoying, though,  they are actually dangerous. 00:17:17.982 --> 00:17:24.598 That's because one of the most common ways people address a smoke detector which keeps detecting erroneous smoke 00:17:24.598 --> 00:17:27.833 is to take it down or otherwise disable it. 00:17:27.833 --> 00:17:32.800 And a disabled smoke alarm is exactly as effective as an imaginary one. 00:17:33.600 --> 00:17:38.210 Photoelectric smoke sensing is much less prone to false alarms. 00:17:38.210 --> 00:17:44.768 They’re not impervious to the problem - as a matter of fact I had one myself which developed a newfound sensitivity 00:17:44.768 --> 00:17:49.998 a few years after I first put it up and started going off  whenever I used the dryer. 00:17:49.998 --> 00:17:57.285 However in that case it was an electric dryer which vented directly into the hallway right where the alarm was 00:17:57.285 --> 00:18:03.087 so it wasn’t an ideal situation from the start. I think moisture probably killed it somehow. 00:18:03.087 --> 00:18:09.040 Anyway, as a more relevant example, since replacing this  alarm near the kitchen with a photoelectric unit, 00:18:09.040 --> 00:18:11.862 I haven’t had a single nuisance alarm. 00:18:11.862 --> 00:18:14.378 And that was well over a year ago at this point. 00:18:14.720 --> 00:18:16.785 So where does this leave us? 00:18:16.785 --> 00:18:18.400 The answer seems kinda murky. 00:18:19.040 --> 00:18:26.080 Ionization smoke alarms work very well in specific  circumstances, but hardly work at all in others.   00:18:26.080 --> 00:18:31.040 They’re also more prone to false alarms which  may make occupants more likely to disable them.   00:18:32.000 --> 00:18:37.920 Photoelectric alarms outperform them in smoldering  fires and are less prone to false alarms,   00:18:37.920 --> 00:18:42.268 but they aren’t quite as good at alerting you to fires-in-progress. 00:18:43.421 --> 00:18:45.159 So what should you do? 00:18:45.159 --> 00:18:48.582 Personally, I don’t think ionization smoke alarms 00:18:48.582 --> 00:18:54.832 present enough of a performance difference in active fires  to justify their continued use at all.   00:18:55.280 --> 00:19:03.131 Since 2008, the International Association of Fire Fighters has recommended against the use of ionization alarms, 00:19:03.131 --> 00:19:09.242 and as I’ve already said, some authorities have taken action and mandated the use of photoelectric alarms. 00:19:09.242 --> 00:19:15.612 In fact, an ever-increasing number of authorities across the globe, including some US states. 00:19:15.612 --> 00:19:22.193 But ionization alarms are still routinely sold in other places, including my home of Illinois. 00:19:22.193 --> 00:19:27.311 And unless you know what the differences between the two technologies are, 00:19:27.311 --> 00:19:30.235 you probably haven’t paid any attention to this. 00:19:30.235 --> 00:19:33.925 Making matters worse is that many alarms  that are out there in the wild 00:19:33.925 --> 00:19:37.164 don’t make it clear what technology they use. 00:19:37.164 --> 00:19:43.154 If you take a look at the ones on your ceilings or walls, there may be no indication at all! 00:19:43.154 --> 00:19:49.974 These brand new alarms, which are photoelectric, don’t say that anywhere except the box! 00:19:49.974 --> 00:19:56.630 This brand-name ionization alarm does say it’s ionization on the back, so that’s good I guess. 00:19:56.630 --> 00:19:59.904 The combo alarm also says it’s both. 00:19:59.904 --> 00:20:03.920 To tell what you have, take it off  the wall and see if there’s a label somewhere. 00:20:04.480 --> 00:20:09.360 Hopefully there is but if there isn’t, well  if you can see the insides of the alarm the   00:20:09.360 --> 00:20:16.283 ionization chamber is a pretty recognizable thing; usually it's some sort of cylinder and will have a radiation label on it, 00:20:16.283 --> 00:20:19.737 but it’s not always possible to get at the insides. 00:20:19.737 --> 00:20:20.982 [voiceover] Two quick things; 00:20:20.982 --> 00:20:26.240 I was apparently wrong about  there being a radiation label on the sensor body itself, 00:20:26.240 --> 00:20:31.927 and, speaking of the sensor body, the ionization  chamber didn’t quite look like what I expected it to 00:20:31.927 --> 00:20:35.120 since apparently the outer shell  forms one of the electrodes these days. 00:20:35.680 --> 00:20:41.221 Such are the perils of writing a script and  shooting the talky bits before actually taking the things apart. 00:20:41.221 --> 00:20:44.765 However, at least here in the US, if it’s an ionization alarm 00:20:44.765 --> 00:20:49.612 there’s probably gonna text regarding the fact that there’s americium-241 in there, 00:20:49.612 --> 00:20:52.537 with permission from the Nuclear Regulatory Commission. 00:20:52.537 --> 00:20:57.961 I don’t know what labels you might find in other countries, but if you see a warning about radioactive material, 00:20:57.961 --> 00:20:59.280 that’s an ionization alarm. 00:20:59.920 --> 00:21:07.227 Now, there is still the fact that ionization alarms may still be faster at alerting you to a sudden, flaming fire. 00:21:07.918 --> 00:21:15.337 It just doesn’t look to me and many other like this potential benefit outweighs the various downsides of the technology. 00:21:15.337 --> 00:21:20.408 However if you think it’s valuable to have an ionization alarm just in case, 00:21:20.408 --> 00:21:27.040 my recommendation would be to purchase a separate alarm and make sure to place it far away from your kitchen to prevent nuisance alarms.   00:21:27.760 --> 00:21:35.278 I personally wouldn’t trust one of these combo alarms because  it's just too unclear how the sensors actually get used in the logic - 00:21:35.278 --> 00:21:40.081 and two separate alarms are usually cheaper than one of these, anyway. 00:21:40.081 --> 00:21:47.520 For what it’s worth, I didn’t replace one of the ionization alarms here because it’s far enough from the kitchen to not be affected by cooking   00:21:47.520 --> 00:21:52.268 and having photoelectric alarms elsewhere makes me feel plenty safe. 00:21:52.268 --> 00:21:58.356 But when it’s no longer functional, I will probably go with a  photoelectric alarm to replace it. 00:21:58.356 --> 00:22:04.240 I don’t know if I would go so far as to call the ionization  chamber an obsolete form of smoke detection,   00:22:04.240 --> 00:22:06.553 but it’s definitely flawed. 00:22:06.553 --> 00:22:09.600 The more people that are aware of its weaknesses, the better. 00:22:10.496 --> 00:22:16.124 Before I go, you’ve probably seen recommendations  to replace smoke alarms every 10 years. 00:22:16.124 --> 00:22:23.533 In fact, these days smoke alarms with single-use  lithium cells which are designed to last 10 years are pretty common - 00:22:23.533 --> 00:22:27.963 and in some places, those are the only battery-operated kind available. 00:22:27.963 --> 00:22:32.342 Now, the recommendation has nothing to do with the americium. 00:22:32.342 --> 00:22:39.839 The half life of americium-241 is over 400 years,  so the sensor could easily outlive you. 00:22:39.839 --> 00:22:44.560 Instead the recommendation is to guard against  aging electronics causing unit failure. 00:22:45.520 --> 00:22:52.181 I’m sorta on the fence about this, because 10  years is a pretty dismal life expectancy. 00:22:52.181 --> 00:22:58.221 But on the other hand, these are cheap  and cheaply made so maybe it’s fair. 00:22:58.560 --> 00:23:06.195 What I wish were far more common was  actually testing your smoke alarms with a canned smoke product. 00:23:06.195 --> 00:23:11.094 Commercial fire alarm systems get  their smoke sensors actually tested this way. 00:23:11.401 --> 00:23:16.492 You might have seen someone going around with a little  spray can of magic smoke and puffing it into the sensors 00:23:16.492 --> 00:23:20.830 while radioing someone else at the  control panel who's looking for a response. 00:23:21.840 --> 00:23:25.977 It seems to me like cans of that stuff ought  to be available for the home 00:23:25.977 --> 00:23:28.531 and that we should be recommending using it. 00:23:28.531 --> 00:23:31.622 I mean, I’m sure you can find the stuff online somewhere 00:23:31.622 --> 00:23:36.598 but it has always seemed odd to me that we don’t recommend that strategy for the home. 00:23:37.280 --> 00:23:41.462 Seems to me like actually proving operation  of the sensor bit 00:23:41.462 --> 00:23:45.040 is more valuable than hitting a button and making sure it starts beeping. 00:23:46.064 --> 00:23:48.978 But what do I know, I just make YouTube videos. 00:23:49.925 --> 00:23:52.464 ♫ alarmingly smooth jazz ♫ 00:23:54.615 --> 00:23:57.666 Let me tell you, eve - well, that’s uh… 00:23:57.666 --> 00:23:58.702 [clears throat] 00:23:59.112 --> 00:24:02.116 I wrote it as “let me tell you” but I wanted to say it as “let me tell ya” 00:24:02.116 --> 00:24:04.696 and it’s those little details that’ll trip ya up. 00:24:04.696 --> 00:24:09.722 Well, that smoke alarm [clunk] which is now… yeah. 00:24:09.722 --> 00:24:11.960 Consult your local file ath…. 00:24:14.080 --> 00:24:16.033 File authority! 00:24:16.033 --> 00:24:17.142 Consult your local 00:24:17.142 --> 00:24:21.867 fileafloridaeyhamorffhhaffifceuuuigigrechoirmeninyourarea 00:24:21.867 --> 00:24:27.474 That knocks loose some of their electrons, resulting in some gas charged mole … frark! 00:24:27.474 --> 00:24:30.627 When those smark… smark porticles? 00:24:31.440 --> 00:24:35.806 That may have been why just using the oven was  prone to causing this alarm. 00:24:35.806 --> 00:24:37.194 To alarm. 00:24:37.194 --> 00:24:38.430 Shoot. 00:24:40.735 --> 00:24:45.093 You didn't actually pause the video and check your alarms, did you? 00:24:45.093 --> 00:24:48.900 Well, here I am again tell you to do it. 00:24:48.900 --> 00:24:52.264 The video's over now, you don't have any more excuses. 00:24:52.264 --> 00:24:53.906 DO IT.