Humidity readings may differ slightly between your Blueair humidifier and other hygrometers. There are many factors that can affect the humidity reading and humidity sensors can vary by ±5% or more depending on:

• Sensor quality
• Placement (near windows, vents, or doors)
• Height from the floor
• Proximity to the humidifier output

For best accuracy:

• Place sensors away from direct airflow
• Avoid placing them right next to the humidifier
• Allow several hours for readings to stabilize after adjustments

Small differences between sensors do not necessarily indicate a performance issue.

• It depends on your target humidity setting as well as the humidity in the room
• In cold dry winters or hot dry climates, the water tank will need to be refilled more often
• For moderate environments, the water in the tank may last a few days
• In humid environments, your tank may not fully empty regularly, but water should be changed out weekly
• Please see detailed run time information in product info section

The short answer is that this is because the humidifier is working harder.

In dry conditions like cold winters or hot dry climates, more water is absorbed into the air and at a faster rate. This increased water usage is actually a sign that the humidifier is actively humidifying, not a defect, and will deplete the water in the humidifiers tank more rapidly.

In more humid seasons, the same tank may last significantly longer because the air can’t absorb as much additional moisture.

This is normal in dry environments.

In cold winters or hot dry climates, a 5–10% increase in relative humidity can actually represent a significant amount of added moisture—especially in a room where moisture is constantly being pulled out by dry air and heating systems.

The humidifier is adding water continuously, but the environment is also continuously removing it. Like filling a bucket with a hole in the bottom.

Cold winter air holds far less moisture than warm air. When cold outdoor air enters your home and is heated, its relative humidity drops dramatically.
For example:

• Cold outdoor air at 30°F can hold less than half the moisture of indoor air at 70°F
• When that air is heated indoors, it becomes extremely dry
• Your humidifier must constantly replace moisture being lost through ventilation, drafts, and normal air exchange
  

 

This is why humidity levels often plateau in winter, even after running the humidifier overnight.

Very dry environmental conditions, like cold winters or hot dry climates, can make it very difficult to raise indoor humidity levels—even when the humidifier is working correctly.

A humidifier adds moisture to the air at a fixed maximum output rate. In dry conditions (especially when your home’s heating or cooling system is constantly running), moisture is being removed from the air faster than usual. This can limit how high the humidity level can rise, even in small rooms.

Factors that can prevent reaching your humidity target:

• Very cold outdoor temperatures
• Continuous indoor heating
• Dry incoming air from outside
• Natural air leaks around doors, windows, and walls
• Large temperature differences between indoor and outdoor air

In these conditions, maintaining 30–40% relative humidity is often realistic, while higher settings may not be achievable. 

Seasonal changes and your local climate greatly affect your home's humidity. For a comfortable and healthy home, aim for a humidity level between 30-50%.

• When the air in your home is too moist, it can feel hot and sticky, and it can worsen health conditions like asthma and allergies, making it more difficult to breathe.

• On the other hand, when the air is too dry, you might notice dry skin, an irritated throat, or itchy eyes. Low humidity can also damage wood floors and furniture, causing them to warp or crack.

  • Dry: <30%

  • Ideal: 30-50%

  • Moist: >50%

An evaporative humidifier uses a fan to blow air through a moistened wick filter, causing water to evaporate into the air and increase humidity.

The wick filter should be replaced every 6 months. It should be cleaned weekly when in use according to the instructions in the user manual to maintain optimal performance.

Important! When the wick filter is replaced, the Filter Expire Indicator must also be reset. To reset your Filter Expire Indicator:

1. Extra long-press the fan speed button for about 15 seconds until LEDs on the interface light up, then release.
2. If done correctly, the wick filter replacement indicator will blink three times and then disappear.

Important! Turn the humidifier off and disconnect from the power supply before maintenance.

When your humidifier's indicator light turns red, it's time to change the wick filter.

You may need a humidifier in your space if you experience low humidity.

Signs of low humidity can include dry skin, an irritated throat, itchy eyes, or static electricity. Low humidity can also damage wood floors and furniture causing them to warp or crack. As general rule, it is important to maintain an indoor humidity level between 30-50%

To reset the filter indicator, turn the device on and long press the fan speed button for about 15 seconds, until the LEDs blink 3 times, and then release.
When the wick filter is replaced, the Filter Expire Indicator must be manually reset.

Your Blueair humidifier is safe to use with clean water of your choice, including tap. It is recommended that the water tank be cleaned weakly to ensure proper operation. After refilling press any button to restart.

Option 1: Top Pour (Recommended)

• Turn the device to standby/off
• Carefully pour water straight down the top grill, avoiding the waterproof display
• note: Do not fill past the max fill line
• Before filling the water form the top, ensure the fan is not running.

Option 2: Bucket Fill

• Remove the water tank and flip up the handle allowing you to carry it to a faucet.
• Take off the upper body of the humidifier as well as the wick filter to access the bottom tank
• Note: Do not fill past the max fill line as marked on the water tank

• Long press the display lock button for about 2 seconds (until all the LEDs of the interface light up and blink once). Then release.
• When the Display lock is on the humidifier will continue to operate but all buttons will be locked.
• To unlock, hold down the button again for about 2 seconds until the lights flash and buttons are functional.

*display lock can also be enabled/disabled through the app*

You can adjust the brightness of the display on the unit by pressing the Fan Speed button and On/
Standby button simultaneously. Keep holding the On/Standby button and tap the Fan Speed button to
adjust brightness. If the brightness is at the lowest level, it will increase by one level. If it’s at the highest level, it will decrease by one level.

You can also adjust the brightness using the Blueair app.

The runtime of your humidifier on a full tank can vary greatly depending on the size of your space and the natural humidity in your environment. We recommend keeping a closer eye on the tank when you first get the humidifier and when seasons change to understand how often replacement is necessary in your space.

If the low water light hasn't turned off after filling the water reservoir, manually adjust the fan speed on the humidifier by pressing the fan speed button on the device or through the Blueair app. This will draw water into the pump and allow the sensor to detect the recently added water. The low water indicator will then turn off, and you can see the fan back to your desired speed or return it to Auto mode.

Auto Dry Mode or “Auto Dry” makes life easier by using low airflow to dry out the wick filter after use, so you spend less time cleaning. Your device will automatically switch to Auto Dry Mode 5 minutes after either the water tank becomes empty or the device is turned off.

Note: When turned on, Auto Dry Mode will activate for 2 hours. There is a 5-minute delay before Auto Dry Mode is activated. You can exit Auto Dry Mode or disable this feature in the app if desired. For best hygiene and user experience, we recommend leaving this feature activated.

Humidity readings may differ slightly between your Blueair humidifier and other hygrometers. There are many factors that can affect the humidity reading and humidity sensors can vary by ±5% or more depending on:

• Sensor quality
• Placement (near windows, vents, or doors)
• Height from the floor
• Proximity to the humidifier output

For best accuracy:

• Place sensors away from direct airflow
• Avoid placing them right next to the humidifier
• Allow several hours for readings to stabilize after adjustments

Small differences between sensors do not necessarily indicate a performance issue.

• It depends on your target humidity setting as well as the humidity in the room
• In cold dry winters or hot dry climates, the water tank will need to be refilled more often
• For moderate environments, the water in the tank may last a few days
• In humid environments, your tank may not fully empty regularly, but water should be changed out weekly
• Please see detailed run time information in product info section

The short answer is that this is because the humidifier is working harder.

In dry conditions like cold winters or hot dry climates, more water is absorbed into the air and at a faster rate. This increased water usage is actually a sign that the humidifier is actively humidifying, not a defect, and will deplete the water in the humidifiers tank more rapidly.

In more humid seasons, the same tank may last significantly longer because the air can’t absorb as much additional moisture.

This is normal in dry environments.

In cold winters or hot dry climates, a 5–10% increase in relative humidity can actually represent a significant amount of added moisture—especially in a room where moisture is constantly being pulled out by dry air and heating systems.

The humidifier is adding water continuously, but the environment is also continuously removing it. Like filling a bucket with a hole in the bottom.

Cold winter air holds far less moisture than warm air. When cold outdoor air enters your home and is heated, its relative humidity drops dramatically.
For example:

• Cold outdoor air at 30°F can hold less than half the moisture of indoor air at 70°F
• When that air is heated indoors, it becomes extremely dry
• Your humidifier must constantly replace moisture being lost through ventilation, drafts, and normal air exchange
  

 

This is why humidity levels often plateau in winter, even after running the humidifier overnight.

Very dry environmental conditions, like cold winters or hot dry climates, can make it very difficult to raise indoor humidity levels—even when the humidifier is working correctly.

A humidifier adds moisture to the air at a fixed maximum output rate. In dry conditions (especially when your home’s heating or cooling system is constantly running), moisture is being removed from the air faster than usual. This can limit how high the humidity level can rise, even in small rooms.

Factors that can prevent reaching your humidity target:

• Very cold outdoor temperatures
• Continuous indoor heating
• Dry incoming air from outside
• Natural air leaks around doors, windows, and walls
• Large temperature differences between indoor and outdoor air

In these conditions, maintaining 30–40% relative humidity is often realistic, while higher settings may not be achievable. 

Seasonal changes and your local climate greatly affect your home's humidity. For a comfortable and healthy home, aim for a humidity level between 30-50%.

• When the air in your home is too moist, it can feel hot and sticky, and it can worsen health conditions like asthma and allergies, making it more difficult to breathe.

• On the other hand, when the air is too dry, you might notice dry skin, an irritated throat, or itchy eyes. Low humidity can also damage wood floors and furniture, causing them to warp or crack.

  • Dry: <30%

  • Ideal: 30-50%

  • Moist: >50%

• The wick filter may develop a white or yellow buildup after some use. Mineral deposits and other debris, that originated in the water used to fill the humidifier, that have been trapped by the wick filter cause this buildup and staining.

• To clean, remove the wick filter from the filter cage and rinse under running water. For a deeper clean, soak with mild or citric acid cleanser, 20g citric acid for every 1L of water for 1 hour, then rinse well under running tap water according to the instructions in the user manual.

Humidity levels can vary within the same room due to several factors. One primary reason is the distribution of air flow. Areas closer to air vents, windows, or doors might experience different humidity levels compared to more central parts of the room. This is because air circulation can cause uneven distribution of moisture.

Another factor is the presence of moisture sources. For example, the placement of the humidifier itself or a water source like a sink or plants in one part of the room might drive higher humidity levels compared to other parts of the room
Lastly, the type and placement of humidity measuring devices can affect readings.

Different devices might have varying levels of accuracy, and their placement can influence the readings they provide. For instance, a device placed near a window might show different humidity levels compared to one placed in the center of the room.

If the water is at the max fill line prior to installing the pump, the slight displacement cause by inserting the pump will not cause an issue.

The Blueair H35i humidifier uses evaporative technology which pulls water molecules from the wet wick filter and dispenses it into the air, there will be no visible mist coming from the device.

Possible causes as to why your humidifier appears to not be working:

• The humidifier has run out of water in the tank. Check if the “low water” icon is turned on and add more water to the tank
• The humidifier is in Auto Mode and the target humidity level has been reached. Check the interface or app to see if target humidity has been reached. If so, the unit will go into standby.
• The 3 pin connector between the pump and top are misaligned or unconnected. Remove top and make sure to align the dot on the top with the dot located on the water tank above the max fill line.

Potential Causes:

• Temporary Wi-Fi disturbances.
• New Wi-Fi settings or router.

If your humidifier does not re-connect by itself after a few minutes:

1. Open the Blueair app.
2. Select your humidifier and go to Product Settings.
3. Delete the humidifier.
4. Go back to the home screen and select “Connect Product”. Follow the connection instructions on the product.

Ensure that the room the humidifier is operating in is appropriately sized for the device's capacity, ensure doors and windows are closed, and verify the hydrometer is working correctly.

If your device is set to Auto Mode, the target humidity level may have already been reached. Increase the target humidity level or exit Auto mode and use manual operation by selecting a Fan Speed.

• Possible cause – the humidifier is too far from your phone and router during set up

1. Ensure that your phone, humidifier, and Wi-Fi router are in the same room and in a close distance during the initial set up (follow the app for exact distance instructions). Once you have successfully paired your humidifier, you can place it at your desired location.
2. Make sure your humidifier is plugged in and powered on.

• Possible cause – The Blueair App is not up to date

Open the App Store on your smartphone and ensure you have the latest Blueair app version

• Possible cause – The router is not on or has no connection. The router is not using a standard connection.

Ensure the following before trying to connect:

1. The Internet is currently running
2. You are using a 2.4 GHz network
3. VPN is disabled.

A factory reset can resolve issues with your air purifier or restore the device to its original settings. Please note that a factory reset will reset the filter timer and disconnect the air purifier from the Blueair app.

Steps to Perform a Factory Reset:
Press and hold the On/Standby button for approximately 15 seconds until all LEDs blink four times, then release. The humidifier will enter Standby mode once the factory reset is complete.

Important: After a factory reset, your humidifier will appear offline, which is normal. To reconnect, open the Blueair app, select "Connect," and follow the on-screen instructions to reconnect your humidifier.