Can a Humidifier Set Off a Smoke Alarm?

Smoke alarms are small devices that detect smoke and help you to take action early enough to avoid a fire outbreak. Having a smoke alarm or a smoke detector in your home or office or any other establishment is an important safety measure.

The smoke alarms detect smoke particles and then light a beam that sets off the alarm. Nevertheless, sometimes your ionization smoke alarms may give you false alarms. Given that the modern home is full of gadgets, including the air conditioner and humidifier, it is important to know whether a humidifier can set off the smoke alarm.

Can Humidity Affect Smoke Alarms? 

Smoke alarms are designed to detect dense particles and then set off a chain of processes, including triggering the light beam, before setting off the actual alarm.

In practice, your smoke detectors may fail to differentiate between ionized air from the presence of smoke and humidity from your cool mist humidifier.

Therefore, instead of detecting flash fires, your smoke detector may go off when it senses the water molecules that come from your humidifier. This, in other terms, is an example of false alarms.

Humidity Setting Off Smoke Detector – At What Humidity Setting does Smoke Detector Get Triggered?

Your fire safety sensors can go off and set off false alarms when the humidity level in your home is about 85%. This means as the cool mist humidifier or any other type of humidifier that you may have in your home maintains the process of releasing mist, the ionization smoke alarms may easily confuse the density of the mist particles for smoke and trigger a false alarm.

Ionized Smoke Alarms 

Ionization smoke alarms are a special type of smoke alarm. There are two types of smoke detectors, based on how they work: ionization smoke alarms and photoelectric smoke alarms. Ionization smoke alarms are by far the better in detecting flash fires. These types of fire detectors are also particularly good in detecting fires that start after a long period of smoldering.

Ionization smoke alarms have a chamber that contains two plates. The plates produce a low-level current that ionizes the air between them. The ionized air maintains a steady flow of current between the two plates.

When your humidifier releases water particles that fill the entire house, the moisture particles interfere with the flow of electric current between the two plates of your ionization smoke alarms. This process sets off the humidifier trigger that sends false alarms. When this process takes place, you may end up calling the fire marshals in panic.

Photoelectric Smoke Alarms 

A photoelectric smoke alarm has a chamber that contains a light sensor in one compartment and a source of LED light in another compartment. The source of LED light in one compartment shoots a straight beam of light across the two ends of the compartment. Under ideal conditions, the beam of light keeps shining from one end to another.

When the straight beam of light is interfered with, the LED light scatters in different directions. When the photosensor in another compartment detects the beam of LED light from the other compartment, it sets off the alarm.  This is particularly common when you have a long-smoldering fire in the building.

Water particles from your humidifier can interfere with the beam of light from the sensor just as smoke particles from a smoldering fire. When the water particles from the humidifier enter the light chamber, they cause the beam of LED light to scatter outside the chamber.

The scattered beams of light from the LED beam end up in the chamber that contains special light sensors. The photosensors may then trigger the alarm.

Can a Humidifier Trigger a Smoke Alarm? 

A humidifier can trigger a smoke alarm when there is high humidity in your house or particularly in the area near the smoke alarm. Your humidifier works by increasing the amount of moisture in the air. It is necessary to use a humidifier particularly during the time when the air is dry and cold.

Humidifiers help to make the indoor environment comfortable by ensuring that the relative humidity levels are within the recommended standards.

However,  humidifiers can trigger the fire alarm becuase of the nature of their functioning. If you have an ionization fire alarm, the humidifier may trigger it to go off. This happens because the water particles from the humidifier interfere with the flow of current between the two detector plates of the fire alarm.

When the flow of the small electric current between the two plates is interfered with, the ionization smoke detector fails to differentiate between the water and smoke particles.

If you have a photoelectric smoke alarm, the presence of humidity from your humidifier may trigger the device to set off a false fire alarm. When the particles from your humidifier enter the chamber that contains the LED light beam, they scatter the beam just like the smoke part. Thus, the scattered light beam ends up in the chamber that contains the photosensors. The photosensors then set off the process of raising an alarm.

One of the main reasons why humidifiers trigger the fire alarm relates to the amount of humidity in the atmosphere. Humidifiers do not trigger off the fire alarms every day.

Given that you may have to use your humidifier every day when it is necessary, it is important to understand the conditions under which the humidifier triggers the smoke detectors. It is common for this to occur when the humidity levels in your house or near the smoke detector are higher than 85%.

It is common for the humidifier to trigger the smoke detectors if the smoke detectors are close to the bathroom. Steam from the bathroom may combine with the mist from the humidifier to dramatically increase the relative humidity levels in your house to higher than 85%. When this happens, the smoke detectors may go off, triggering a false fire alarm.

How to Stop Smoke Alarm Going Off Due to Humidity? 

Humidifiers are necessary for the modern home or any other premises. They are especially useful during weather conditions when the air is dry. However, these little devices can set off false alarms quite often.

You cannot avoid using your humidifier because of the risk of them setting off the false alarm. Therefore, you need to understand how to stop your fire alarm from going off because of detecting the mist from the humidifier.

Here are a few tricks that you can use to prevent the smoke alarm from going off due to humidity.

  • Keep the humidity levels low: One of the most effective ways of keeping the humidity levels low is to avoid always using the humidifier. Your smoke detectors will go off when the humidity levels in the house are well beyond 85%. You can prevent this phenomenon from occurring by using your humidifier only when it is absolutely necessary. You may not have to leave your humidifier running throughout the entire night to keep the relative humidity levels low.
  • Adjust the sensitivity levels of your fire alarms: Some modern smoke detectors have the functionality that allows users to adjust their sensitivity levels. If your smoke detector comes with this feature, use it to make the fire alarm less sensitive to the triggers that may be found in your home. However, you need to balance between the need to avoid false alarm and that of ensuring that your fire alarm works perfectly.
  • Keep your smoke detectors in perfect shape: Water particles usually accumulate on the outer casing of your smoke detectors. The presence of such water molecules may trigger your smoke detector to give off false alarms. Therefore, it is wise to keep the outer casing of your smoke alarms completely free of any water molecules. Regular cleaning of the outer casing will go a long way in ensuring that you do not encounter false fire alarms.
  • Keep and use the two types of fire alarms: Photoelectric fire alarms differ from ionization fire alarms in terms of their level of sensitivity. If you keep the two types of smoke detectors and use them concurrently, you will be able to tell when one of them goes off because of a false trigger. Using the two types of fire alarms will help you avoid calling the fire marshals unnecessarily when there is no fire in your home.


Fire or smoke detectors are an essential aspect of your home. They can help you forestall disasters when there is a fire because they provide an early warning system. However, they can be quite annoying when they go off if there is no real fire in your home.

These devices are unable to differentiate between water molecules from the humidifier and the smoke particles from a long-smoldering fire. Thus, you need to take a few measures to ensure that they do not go off when the humidity levels are exceptionally high.

One trusted method of achieving this objective is to ensure that the humidity levels in your home or any other premises do not exceed 85%. Also, you may use both types of smoke detectors to reduce the chances of false positives.