Air Quality Levels in PuffiAir

PuffiAir internally evaluates air quality and classifies it into 3 levels:

Level	Label	Description	MQTT status
🟢 Normal	normal	All readings within safe range	normal
🟡 Warning	warning	One or more values close to threshold	warning
🔴 Danger	danger	One or more values exceed danger threshold	danger

The status is published via MQTT to:

puffiair/status
Payload: "normal", "warning", or "danger"

How Are Levels Determined?

Each sensor reading is individually compared to a threshold range. The overall level is based on the worst sensor status.

PuffiAir determines the current air quality level as normal, warning, or danger by evaluating multiple sensor inputs. The thresholds are defined in firmware and are applied only to PM2.5, CO₂, VOC index, and gas ADC value. PM1.0, PM4.0, and PM10 are measured and displayed but do not affect the status level.

Sensor	Measured Unit	warning if ≥	danger if ≥	Reference
CO₂	ppm	1000 ppm	1500 ppm	ASHRAE / WHO
PM2.5	µg/m³	35	75	WHO 2021 Guidelines
VOC Index	unitless index	120	300	Sensirion VOC Algorithm
Gas ADC	analog ADC value	1500	3000	Internal calibration

Gas Sensor Notes

The gas sensor used in PuffiAir (MICS5524) is a general-purpose air quality sensor. It reacts to a broad range of combustible gases (e.g., methane, CO, ethanol), but does not provide gas type discrimination or precise PPM values.

• The gas_adc value represents raw analog voltage, which increases in the presence of certain gases.
• Thresholds are defined based on Puffilab's internal calibration, reflecting relative air quality degradation rather than specific pollutant levels.

Sensor	Meaning	warning if ≥	danger if ≥
gas_adc	Raw gas reactivity (no units)	1500	3000

Warning

Disclaimer: This gas sensor is not certified for safety-critical applications (e.g., gas leak detection). It is intended to provide environmental awareness and support overall indoor air quality evaluation.