The humidity inside my home seems to trigger the smoke alarms.
Any one have a solution short of disabling them?
First, are they ionization or photoelectronic smoke detectors?
Second, is it actual humidity or “fog” from a shower, wash basin, etc., that sets them off? In other words, do they go off when relative humidity is above a certain point, or when you run the shower? These are two entirely different scenarios.
BTW, you’ve made me very happy because I’ve finally found a thread on a subject in which I’m an actual expert (i.e., certified, licensed, and everything).
If ZonexScout is an actual expert, I’ll defer to them. However, I’ll jump in to say that they do make “smoke” detectors that detect heat instead of smoke. I don’t know how those play into code since they’ll probably not go off until it’s too late in many scenarios.
Really, the only time I ran across them is when I started welding. I wanted something for my garage and realized a smoke detector wouldn’t work since the smoke from the welder would set it off. That’s a case where a heat detector would work (or at least help).
Anyways…
My nest smoke detectors say they rule out humidity as a factor, but I believe they’re referring to fog from a shower (though I could be wrong). However, they also start out quieter and give you the ability to shut them off with your phone. FTR, the don’t start off quiet and you can’t shut them off with your phone unless the detector feels confident it’s a nuisance alarm.
…and before I hit send I did a little looking and I see that high humidity (getting up over 90%) will set off ionization type detectors, so maybe that is it.
Lastly, before looking for a way to temporarily disable it, I’d look into replacing it. Feel free to take any advice that ZonexandScout has about what type(s) to replace it with, but unless you’re living in the jungle, I’d be surprised if a properly functioning alarm is going off from ambient humidity.
We had smoke detectors in Bangkok. Talk about high humidity! They never set off accidentally and were just fine.
They are ionization and go off in the middle of the night when the humidity seems to rise, not from showing.
I’d consider replacement with a CO detector, in the domestic environment. Code dependent, of course
Not an expert by any means, but I did used to live in a college tutor flat where they had smoke detectors in every room, including just outside the bathroom. Whenever I had a shower with the door open, the steam would trigger the alarm. This was a problem, because any time an alarm got triggered anywhere in college, the fire brigade would get called.
The fireys did kind of roll their eyes at me (“Who has a shower with the door open???” “Parents of two active toddlers, that’s who…”) - but they also did agree to change out the smoke detector for one that didn’t do that. So it can’t have been too hard or expensive!
Ionization detectors use a small piece of radioactive material to ionize the air in two chambers, a sealed reference chamber and an open sampling chamber. Small particles entering the sample chamber will impede current flow through the ionized air. When the current flow in the sample chamber differs from that in the sealed reference chamber, the unit goes into alarm.
Humidity (i.e., simple water vapor) usually won’t set them off. There are a couple conditions in which it will. First, if the unit is much cooler than the surrounding air, water vapor may condense on the metal in the sample chamber and trigger an alarm. This sometimes happens when a detector is exposed to cool air from an AC vent continuously or is mounted to a cold surface (e.g., mounted to a ceiling where the attic is not heated and it is winter). Of course, moisture could also condense directly on the unit’s circuit boards. Second, if there is debris in the sampling chamber, humidity could affect that enough to cause the required change in current flow in that chamber.
The simplest thing to do is to replace the detectors. In many jurisdictions, a permit is not required to do this, as you are replacing existing broken detectors in kind. If they are 120VAC detectors, they are mounted to standard electrical boxes and just about any standard detector will fit without modification. Current Codes require that all detectors be interwired to produce the audible alarm when any single unit detects smoke, so you should also have some common wire(s) going between detector locations. Think “hot, neutral, ground, and another wire or two between boxes.”
I would recommend going to photoelectronic smoke detectors. They generally resist ambient conditions better than ionization detectors. One exception is “fog” from showers. Water vapor itself is invisible, but water droplets in suspension in the air are visible and will set off a photo. That’s why we keep all smoke detectors at least three feet from the door to a bathroom. And it is possible that a photo smoke detector can be cooled enough for water to condense on the light sensor or light source, so do keep an eye out for that.
These photoelectronic units often come with battery backup and can be purchased on-line for $40-$80, depending on how fancy you need them to be or whether you want certain features. Takes a couple minutes to install one.
One last warning, many units being imported into the US now are advertised as “meeting” the UL standards, but are not actually listed by UL (i.e., there is no UL mark on the unit or on the instructions). Be sure to get units that are actually UL-listed, with mark and all.
I know a lot of posters claim to be an expert in subject X, but I’m a professional consultant in fire alarm and life safety systems and have been for over 20 years. (No, I don’t come around and sell smoke detectors door-to-door.) I’ve actually been accepted as an expert witness by some State and Federal courts. I also teach FA courses related to licensing and professional certification in fire protection technology.
The installation of smoke detectors in garages is prohibited by NFPA 72 (2013). Heat detectors are not permitted to be substituted for the smoke detectors required for installation in each bedroom and outside each sleeping area.
I agree with my colleague Zonexandscout
I have worked in the fire alarm field for 38 years. Ionization smoke detectors in a home setting are definitely prone to false alarms, and they are not very efficient at detecting thick smoke.
This six minute video The Aquarium Test explains this difference very well.
Thanks, Longhair75. You’ll probably recall the tests that were conducted in the abandoned FL motel some years ago, where photos actually reacted faster to typical fires than did the ionizations, especially with dense smoke (particles => 5 microns).
For everyone else, ionizations are extremely sensitive to small airborne particles and solvents. (Want to set off an ionization? Use some ammonia right below it.) That’s why broiling your steak in the oven sets them off every time.
Smoke detectors don’t really “wear out.” They get dirty. Dust, pollen, sheetrock dust (often blown into the detector from the mounting surface because the installer didn’t seal the back of the detector), insecticide residue, and other materials accumulate in the sampling chamber and affect performance. Older detectors get flaky as they get dirty. In many cases, a new, identical unit will fix the problem…at least for a period of time.
Thanks for all your help. Why do they always go off in the middle of the night? Every one seems to have their false alarm problems around 2 am. Do you think smoke alarms will ever become reliable? The reviews I read on all kinds of detectors are awful.
My home has a steel frame, concrete walls and a metal roof. Nothing really to burn, so for now, I’ll take a chance and disable the detectors I have now and wait until technology catches up with the false alarm problem.
Good quality smoke detectors are actually quite reliable. I work a lot with big commercial clients, where a false alarm will dump the building and stop work, often incurring thousands of dollars in lost time and production. My clients are pretty motivated to reduce nuisance alarms. I’ve sometimes worked for days trying to identify and eliminate the problems stemming from just a single detector. (I will get called in to work with the installers, facilities maintenance staff, and risk management team.)
I can’t say why your problem seems to occur more at night. Sometimes the causes are pretty obscure. For example, a smoke detector in a suspended ceiling might have a nuisance alarm when the air in the above-ceiling space goes positive, blowing dust from the ceiling tile down through the detector. Same thing can happen with household detectors mounted to a ceiling below an attic.
I strongly recommend new photoelectronic detectors.
In most areas of the US, it is a non-trivial code violation to disable or remove the required smoke detectors. I’ve been involved in several civil cases where this was a major issue. Please don’t disable them. They could save lives.
Just a hijack:
Why is it prohibited to install in a garage? I can understand why it wouldn’t be advised, but actually prohibited?
NFPA 72 (The National Fire Alarm and Signaling Code) is usually incorporated by reference into State and local building codes. The NFPA is very careful to limit the use of detectors and other equipment where the likelihood of nuisance alarms, or the difficulty of inspecting, testing, or maintaining the devices, outweighs the value of installing the devices. For example, smoke detectors cannot be installed at the tops of elevator shafts unless the shaft is sprinklered. (The idea is that the only good reason to have one there is to shut down power to the equipment and elevator car before the sprinkler activates.)
Garages have multiple sources of nuisance alarms (exhaust, solvents, airborne debris, etc) for smoke detectors. They are also often not suitable for smoke detectors due to air velocity or temperature extremes.
Heat detectors ARE permitted in garages.
Similarly, smoke detectors in residences are not permitted to be within 3’ of an air vent, the tips of a ceiling fan, or the door to a kitchen or bathroom. Detectors within 6’ of a cooking appliance have to be listed as resistant to the cooking fumes and smoke.
I’ll also point out that there is some disagreement about whether smoke detectors can be installed in conditioned garages, where the temperature never gets below 40 degrees F or above 100 degrees F, but that is a pretty unusual situation. Open a garage door when it’s 38 degrees F outside and the inside is going to be 38 degrees F pretty quickly. This is almost never allowed by the AHJ.
Sorry…I didn’t intend to keep posting ad infinitum.
If you are concerned about fire detection in a garage, a rate-of-rise heat detector might be a good solution. They activate when the temperature rises fairly quickly, which is indicative of a fire, rather than waiting until the temperature reaches a fixed point (e.g., 135 degrees F). Much faster response.
Solid information and I would only add that it may be more a symptom of an old detector rather than a limitation of the ionization type detector. Both photoelectric and ionization can be affected by relative humidity levels of 93% and higher. Ionization detectors are more susceptible to “false alarms” due to steam from showers etc. but this does not seem to be the cause here.
My recommendation would be to replace with a new detector, a combination ionization/photoelectric type as that is going to have the highest level of detection capabilities (consider one with carbon monoxide detection as well if there is a source of it in your home). Alternately, a photoelectric type as mentioned.
I smell an opportunity to create some clever Orwellian New Speak here … let’s not think of these as “nuisance alarms” … rather let’s call them “fail-safe alarms” … such that we could say to the OP that their smoke alarm isn’t being a nuisance because it’s, in fact, failing …
They are cheap compared to monthly health insurance premiums …
My experience in the rental business is that smoke alarms most often fail from just being dirty … hopefully, everyone is vacuuming their house on a regular basis, so take the six seconds to vacuum the smoke detector and, hey, another two seconds to test it … once a week please … that smoke detector is there to save YOUR life, please treat it kindly …