Air Quality Monitors - Frequently Asked Questions

Q: Should I use battery or AC power supply

For best results and family protection, we recommend having the monitor plugged into power 24/7. This will allow for uninterrupted air quality monitoring at your home or workplace.

Q: How long the battery should last?

Battery should last for over two hours of continuous monitoring. Battery power is helpful for temporary air quality testing at different areas of your house, car and so on.

Q: Can the battery life be extended?

Some models ( AQ300, AQ300Pro, AQ500) have the option of enabling the screensaver. If enabled, the screensaver will extend the battery life. You may choose between 10/30/60 minutes.

Also, AQ300 and AQ300Pro allow controlling screen brightness. Reducing brightness will increase battery life

Q: Does the monitor require calibration?

Every model of Stellate Air Quality Monitor is factory calibrated

Should the monitor be exposed to high TVOC/HCHO levels for a long period, it will need to be calibrated outdoors. Calibration clears the old values and resets HCHO/TVOC levels back to “normal” levels.

To calibrate, please follow these steps:

1.       Turn the monitor off

2.       Take it outside and turn it on

3.       Let it run for 5 min

4.       Done. You may bring the unit back inside


Q: How does TVOC Measurements work?  

Total Volatile Organic Compounds (tVOC) is one of the most complex pollutants to identify.



Typical # of Carbon Molecules

Compounds Example


Very Volatile Organic Compound

Under C6



Volatile Organic Compound

Between C6  & C16



Semi Volatile Organic Compound

Higher than C16

Diisononyl phthalate (DINP)


Total Volatile Organic Compound

SUM OF ALL compounds  ( VVOC + VOC + SVOC)


The challenge is that VOCs can be emitted by many sources, such as Acetone, Arsine, Benzene, Ethylene glycol, Formaldehyde, Hydrogen sulphide, Methylene chloride, Nitric oxide, Styrene, Tetrachloroethylene, Toluene, and Xylene, etc.

Stellate indoor Air Quality Monitor can only detect the presence of VOC but cannot identify what tVOC sources are.


TVOC Levels

Air Quality Level

TVOC Readings Range



0.000 – 0.5000



0.501 – 1.500



1.501 – 9.999



According to EPA:

Studies have found that levels of several organics average 2 to 5 times higher indoors than outdoors. During and for several hours immediately after certain activities, such as paint stripping, levels may be 1,000 times background outdoor levels.


Q: How does AQI calculated? 

AQI is calculated based on a mathematical formula and determined by the pollutant with the highest index.  For example, if the PM2.5 AQI is 125, the PM10 AQI is 50, and all other pollutants are less than 125, then the AQI is 125–determined ONLY by the concentration of PM2.5. The AQI calculation does not take into account tVOC levels and is calculated differently in different countries since qualifications for “good,” “moderate,” “hazardous,” varies from country to country.

For USA:

Values of Index

Daily AQI Color

Levels of Concern

STELLATE Monitor Display

Description of Air Quality

0 to 50




Air quality is satisfactory, and air pollution poses little or no risk.

51 to 100




Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.

101 to 150


Unhealthy for Sensitive Groups





Members of sensitive groups may experience health effects. The general public is less likely to be affected.

151 to 200



Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.

201 to 300


Very Unhealthy

Health alert: The risk of health effects is increased for everyone.

301 and higher




Health warning of emergency conditions: everyone is more likely to be affected.


From a pollution scientist’s point of view, the AQI/API (Air Pollution Index) is not a very useful number.  In other words, if overall AQI is known, it is impossible to break that number down into component pollutant concentrations.  The AQI is designed for the general public, not for scientific purposes.

Here is an AQI calculator that you may try:

Q: Are HCHO Levels safe in my house? 

Below is the table explaining levels of HCHO:

HCHO air quality grade range

Air quality


HCHO average standard

value (mg/m3)






0.101 – 0.500



0.501 – 1.999



Under normal circumstances, your HCHO level should fluctuate between Excellent and Good levels.

The HCHO level will go over 1 only if you have an excessive amount of formaldehyde at your home.


 Q: How to use Screen Saver and to extend the battery life in AQ500 Model?  

Our recommendation is to have the monitor plugged into power 24/7. This will allow uninterrupted monitoring of your indoor air quality.

By enabling the screensaver, battery life can be extended. You may choose between 10/30/60 minutes. The screensaver will considerably extend the battery life as one of the main consumers of the battery power is an oversized color LCD screen. The monitor is also loaded with multiple sensors and a fan for better air circulation through the monitor.

 When the screensaver is on, the monitor will continue monitoring the air quality and you will be able to see the results by switching to the history screen.

All historical hourly results (up to 8 hours) stored in the corresponding tabs AQI/PM2.5/HCHO/TVOC