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AIR-1 General Tips

The AIR-1 has multiple different types of sensors and this guide will help you understand which ones you should be concerned with and expected safe or not safe thresholds to alert or automate on.

SEN55 Environmental Sensor

The SEN55 is the powerhouse of the AIR-1 with multiple sensors such as particulate matter, volatile organic compounds (VOCs), oxidizing gases, such as nitrogen oxides (NOx), as well as humidity & temperature.

Particulate Matter

Per the EPA: particulate matter (also called particle pollution): the term for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope. Sources of pm particles here.

PM10 : inhalable particles, with diameters that are generally 10 micrometers and smaller; and

PM2.5 : fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.

  • How small is 2.5 micrometers? Think about a single hair from your head. The average human hair is about 70 micrometers in diameter – making it 30 times larger than the largest fine particle.

We suggest triggering alert automations, hvac or a fan turning on, etc when PM particles are rising

This article goes over lots of ways to reduce pm particles in your home!


VOC Index

Per Sensirion,

The VOC Index

describes the current VOC status in a room relative to the sensor’s

recent history. In this way, the VOC Index behaves like a human nose

We suggest triggering alert automations, hvac or a fan turning on, etc when the VOC Index rises above 100

Per Sensirion:

a VOC Index above 100 means that there are more

VOCs compared to the average (e.g., induced by a VOC event from

cooking, cleaning, breathing, etc.) while a VOC Index below 100 means

that there are fewer VOCs compared to the average

VOC Quality

This uses the VOC index and a scale to output an easier to use variable.

0-79: Improved -> 80-149: Normal -> 150-249: Abnormal -> 250-399: Very abnormal -> 400+: Extremely abnormal

We suggest triggering alert automations, hvac or a fan turning on, etc when the VOC Quality changes to Abnormal or Very Abnormal or Extremely Abnormal.

This is a very easy way to automate based on the air quality changing over the past 24 hours but you will still want to automate on particulate matter as well!

NOX Index

Per Sensirion,

The NO x Index describes the current NO x condition in a

room relative to the sensor’s recent history. In this way, the NO x Index

behaves like a human nose.

We suggest triggering alert automations, hvac or a fan turning on, etc when NOx rises above 1

Per Sensirion:

On the NO x Index scale, this offset is always mapped to

the value of 1, making the readout as easy as possible: an NO x Index

above 1 means that there are more NO x compounds compared to the

average (e.g., induced by cooking on a gas stove), while an NO x Index

close to 1 means that there are (nearly) no NO x gases present, which is

the case most of the time (or induced by fresh air from an open window,

using an air purifier, etc.).


SCD40 CO2 sensor

The optional CO2 sensor addon is a great way to add the ability to track CO2. CO2 levels in a closed, poorly ventilated bedroom can quickly rise to concentrations that may impair focus or even pose health risks. Notice the CO2 levels dropping in the image below when the HVAC was turned on overnight!

Wisconsin Department of Health CO2 Level Chart

CO2 Health Department.png

We suggest triggering alert automations, hvac or a fan turning on, etc when CO2 is over 1000

Opening a window, turning on a fan, the HVAC in the house, etc are all great ways to get CO2 to go down!


MiCS-4514 Gas Sensor

The MiCS-4514 is a very unique sensor able to distinguish between multiple gases such as Carbon Monoxide, Nitrogen, Ethanol, Hydrogen, Ammonia, and Methane.