Debate: Ionazation vs Photoelectric Smoke Detectors

So I know this is a big debate in the fire society today and I thought I would like to hear all of your opinions on it. Ionazation or Photoelectric?

I know that Ionazation alarms have being getting a bad rep lately but I can prove that they work. So today, we lit a few candles in a bedroom and eventually the room got so smokey that the detectors went off. My house has Kidde Ionazation smokes about 15 years old. Now, I’m not sure if that can compare to the fact that it took 10 minutes to go off. I guess that Ionazation is good when it comes to smoldering fires with more smoke than flame but they do take a while to activate. They are more likely to tell you when you are a terrible cook and burn your food more than an actual fire.

Photoelectric alarms seem to be the most beneficial, they don’t have nearly as many false alarms and they detect the fire faster. You won’t see these in homes sadly enough simply because everyone goes with the cheapest product which is ionazation.

There are so many variables in a fire that makes it hard to determine exactly which is better. Photoelectric will almost always respond much quicker to a conventional fire, but an ionization could catch a clean burning gas fire early before it gets out of hand.



Dual Technology detectors will always come out on top. They provide the best of both worlds in terms of the scope of protection. They are expensive (believe me, installed 8 of them to replace the old detectors in my house) but could ultimately be a life saver.



Fine details aside, in the end, any smoke detector is better than nothing.


I actually have a photoelectric detector in my room simply because for residential rooms, photo detectors are your best bet. BRK makes them, but you have to dig pretty deep.

I’d have to agree with Nick, that dual-sensor detectors are the best and that any detector is better than no detector.

I’m surprised that dual-sensing detectors aren’t a bigger thing. Seems like it would get rid of the whole issue of whether Ionization vs Photoelectric is better. I guess an issue is that Ionization detectors are a lot more prone to false alarms (at least according to this website), and avoiding false alarms, especially in monitored commercial systems, is really important. That’s probably a big reason why Photo detectors are so prevalent in commercial installations.

So how would the dual detectors work? Also, are the Simplex “FalseAlarms” Ionazation because that would only make sense


Dual-sensor detectors do just what their name describes: they contain both an ionization detection chamber and a photoelectric detection chamber. And TrueAlarms are both ionization and photoelectric, depending on the model number, IIRC. The problem is the detection chamber in them is just downright poor quality.

Ahhhh Classic Simplex and their cheapness. They used to make high quality products like 4251-20s and chevrons but now, downright low quality and full of problems

This goes for everyone, but lets please try to refrain from brand bashing, especially when doesn’t add anything to a post. What kind of basis do you have to make these claims anyway?


Sorry, just got carried away and wasn’t thinking

My parents have Kidde ionization smokes in their house and they go off at least once a week from the oven. They have to take the first floor detector down whenever they cook something.



Compare that to my apartment, which has photoelectric smoke detectors. One is located a few feet from the stove and it has never (knock on wood) gone off from normal cooking activities.

you’ll find multi-criteria detectors in most new commercial buildings these days. they combine photoelectric with thermal sensors and some advanced algorithms to detect false alarms.



the simplex true alarm comes in photoelectric or ionization or heat, or the multi criteria detector that is photo and heat. i’ve never seen both photo and ionization together, it might exist but it isn’t very popular if it does.

We are talking about residential devices, not commercial smokes. For residential they are gaining popularity.

I’m no longer a fan of ionization detectors because of all the cases of false positives and false negatives (false positive = alarm and no fire, false negative = fire and no alarm) that have been reported over the years. Some of these cases have even led to deaths.



A lot of people who get nuisance alarms with ionization or dual sensor detectors often pull them down and remove the battery. Then, the detector ends up somewhere, powered down, after the owner has forgotten about it. I believe this comes from a lack of common sense and reading the paperwork on their detector. People just don’t know how to own a smoke detector. I see a lot of them with dead batteries too since the owners simply forget to put them in. As my dad has always said… No matter what you do you just can’t fix stupid. Smoke detectors do save lives – only if you do your part in keeping them operational so they can do their job.



What I want to see more of is the 10-year sealed battery smoke alarms that Kidde and First Alert have now. I like the idea of paying $30 once for a smoke detector with a battery that should last 10 years. They’re only available in battery powered single station detectors right now though, but I would love to see them start appearing in hardwired detectors as those are required in new construction. The Nest Protect does this already, come to think of it. If you think about it, you can get a cheaper 9V battery powered alarm for like $10 or so ($4 for a Family Gard ionization) but then you have to get a 9V battery for $4. Then you have to change the battery twice a year, so that’s $8 in batteries every year to maintain EACH detector. At the first battery ($4) of the third year you’ve owned the detector, you have exceeded the cost of the $30 sealed battery detector.



I am seeing a marketing change occur with BRK/First Alert, seemingly in favor of photoelectric detectors. The ionization ones are marketed as “Basic Protection” and are in pretty plain packaging while the photoelectric ones are marketed as “Maximum Protection” in very good looking packaging. The photoelectric detectors themselves are sleek and modern (REALLY thin too) – another feature which would appeal to the residential market in my opinion. The ionization ones are the same “fat” design they have been using for over 10 years now. This indicates to me that BRK/First Alert is going to dump ionization sometime soon.



Kidde is the one having the most trouble, IMO – their products are not very well made and most of them contain ionization sensors. In fact, I don’t think you can get a Kidde photoelectric smoke alarm with a CO sensor. I know they do not make a wireless model with a photoelectric sensor. Kidde appears to have turned into one of those companies that is more concerned with profits than good products as I have heard of multiple cases where they sent lobbyists to fight against a proposed ionization detector ban. I’ve stopped buying Kidde products after seeing a decline in their quality, and also after the generally high amount of Kidde fire extinguisher recalls over the last 20 years.



USI Electric is pretty much the king of ionization… I don’t think they make any photoelectric products at all. Good thing they aren’t sold in most retail stores, as far as i know.



As for the last one, Gentex. They do make residential smoke detector products – only hardwired ones though… using a tested and proven photoelectric sensor design that works extremely well. I like the quality of their products and the fact that they are the last smoke alarm manufacturer who manufactures their products in the USA. Everyone else is in China or Mexico…



In fact, only a few commercial brands still make ionization detectors… most do not anymore. System Sensor has recently discontinued their ionization detector product line. I do not think Interlogix (ESL) has ever made an ionization detector, and Hochiki has not made an ionization detector since the early 90s. Apollo still does though. Simplex still has an ionization detector in their TrueAlarm line though. As for Siemens, their website is too frustrating to navigate and I was not able to determine. I’ll tell you from my own experience though that nobody installs ionization detectors in commercial buildings anymore unless they REALLY have to. I work for a Notifier dealer and it’s usually a multi-criteria, a laser based detector, or an air sampling detector used in situations where ionization’s sensitivity to smaller smoke particles is necessary.



In summary I think there’s a lot of ways that residential detectors can be improved such as with the 10 year battery or even bringing in a few of the false alarm prevention features that commercial detectors have. If these brands would focus more on protection of life and property when making new products than on profits, I think that higher quality products would come around.



End rant. lol.

Disposal of ionization detectors is another big problem with them. That whole radioactivity thing they have going isn’t exactly a great thing…



I wouldn’t be surprised if ionization detectors were completely banned in the next 10 years, they already have been in a few states.

I thought you could dispose of them in landfills because it’s in a chamber?

Yeah, those Gentex smokes are nice. Most units in my apartment complex have them to replace dead units and they never have false alarms. Cooking bacon? Doesn’t go off, even though the detector is pretty close to the stove without any shielding.



The Kidde alarms are crap, but that’s what my parents’ house has. Is there any way to hardwire in another brand (with a photoelectric detector) and have it interface with the Kidde units?

they need to be sent back to the manufacturer. usually cities have a place where you can dispose hazardous waste and get rid of them there.

The Ions and other single station Kidde detectors I looked at we not of very good quality, however I was very impressed with the quality of the dual-tech detectors I installed. They have been installed for about a year now and I have not had one problem with them. This could possibly be signaling a turn-around for them too?

my house only has 1 photoelectric detector located in my bedroom on the ceiling (a first alert SA720 W/ escape light)



the rest of my house has 2 first alerts,1 BRK and 1 nighthawk(kidde)



i perfer photoelectric because it detects slow smouldering fires which are more common than fast flaming fires.

The company I work for has a lot of residential high-rises amongst our clients. Since testing insuite smoke alarms is part of our annual inspection process, I’ve had lots of experience thrust upon me lately. (Point of Note: we use Kidde smoke alarm products)



Remember what each type is built to do.

Ionization: detect the invisible gasses which result from fast-igniting fires. (downside: those same gasses can come from opening a hot oven, cooking toast, or even a steamy shower; ergo lots of false alarms)

Photoelectric: detect visible smoke & particulates resulting from slow-smouldering fires. (downside: a quickly igniting fire can do a lot of damage before significant visible particles are present; ergo fires can be missed until too late)

The right tool for the right job is important.



With the modern move towards smaller living spaces & new materials which don’t quickly ignite, ion smokes aren’t very effective. I see many, every single day, that are disconnected because the owner is sick of it going off when they try to cook. By code, a smoke alarm needs to be placed outside the bedroom. In a 500sq.ft. apartment that means it’s right by the kitchen, too, whereas a large house would have the kitchen a ways away from the bedroom(s).



In apartments, photoelectric are what makes sense. Unfortunately, as these units cost $10 more than ions, the rush for maximum profits makes them a rare choice during construction.



As for manufacturers, I haven’t seen a huge difference in quality between them. Kiddie has a large range of options (120v, 120 W/ battery, battery only, 10-yr battery, front loading battery, ionization, photoelectric, carbon monoxide, combinations thereof, talking <French & English>, LED integrated, connectable to strobe, etc, etc) & they’re not too expensive. They’re not the best on the market but not the worst either. In my experience, anyway.



So… as for the photo vs. ion debate, I say make sure you’re using the one that suits the job. They do the same job in different ways; as professionals it’s our job to ensure the right unit is being used. Just remember: our main duty is to try to save lives. That’s the goal we aim for.