Overview

The SGP40 is a digital Volatile Organic Compound (VOC) gas sensor manufactured by Sensirion. Housed in a 2.44×2.44 mm2.44 \times 2.44\text{ mm} 6-pin DFN package, it is designed for indoor air purifiers, HVAC ventilation fans, and smart home air quality monitors.

Built on Sensirion's CMOSens MOX (Metal-Oxide) technology with siloxane resistance, the SGP40 detects airborne organic chemicals, solvents, paints, cleaning agents, human breath emissions, and cigarette smoke. Paired with Sensirion's VOC Index Algorithm, it outputs a continuous VOC Index (0 to 5000\text{ to }500) over I2CI^2C (0x59), where 100 represents normal clean ambient air baseline.

Quick reference

Operating voltage (VIN)3.3 V to 5.0 V DC (breakout includes 3.3V LDO regulator)
IC supply voltage (VDD)1.7 V to 3.6 V DC (3.3 V nominal)
InterfaceI2CI^2C Fast-Mode (up to 400 kHz)
Fixed I2CI^2C address0x59
Target GasesVolatile Organic Compounds (VOCs / Solvents / Alcohols / Smoke)
VOC Index Range0 to 5000\text{ to }500 (100=Clean Air Baseline100 = \text{Clean Air Baseline}, >200=Polluted Air>200 = \text{Polluted Air})
Warm-up Time10 seconds fast warm-up
Heater Power Draw2.6 mA2.6\text{ mA} average operating current
Sleep Current3.0 μA3.0\ \mu\text{A} sleep mode

Pinout

Breakout module header & STEMMA QT / Qwiic connectors:

PinNameTypeDescription
1VINPowerSupply power input (+3.3 V to +5.0 V DC)
2GNDPowerGround reference (0 V)
3SCLDigital InputI2CI^2C Serial Clock
4SDADigital Input / OutputI2CI^2C Serial Data

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply Voltage (Module)VVINV_{VIN}3.33.3 / 5.05.5VPower rail with LDO
Active Supply CurrentICCI_{CC}—2.63.5mAContinuous sampling state
Sleep CurrentIsdI_{sd}—3.010.0µASoftware sleep mode
VOC Index ResolutionResVOCRes_{VOC}—1—Index unitsRange 0 to 500
Response Time (T90T_{90})t90t_{90}—< 10—sStep change in VOC concentration
RepeatabilityRepRep—±5\pm 5—Index unitsAt 100 Index baseline

VOC Index Algorithm & Temperature Compensation

The SGP40 raw output is a 16-bit SRAW_VOC tick count (0…655350\dots 65535). Passing this value along with ambient Temperature and Relative Humidity into the Sensirion C++ / Python VOC Algorithm generates the normalized VOC Index:

  • VOC Index = 100: Clean ambient air baseline (adaptive auto-zeroing).
  • VOC Index 100 – 200: Mild VOC presence (cooking, perfume).
  • VOC Index 200 – 500: Heavy VOC pollution (paints, solvents, heavy smoke).

Wiring

SGP40 Pin→Arduino / MCUESP32Notes
VIN5V / 3.3V3.3VPower rail
GNDGNDGNDSystem ground
SCLA5GPIO 22I2CI^2C Clock
SDAA4GPIO 21I2CI^2C Data

Example (Adafruit_SGP40 Library)

cpp
#include <Wire.h>
#include "Adafruit_SGP40.h"

Adafruit_SGP40 sgp;

void setup() {
  Serial.begin(115200);
  Serial.println("Adafruit SGP40 VOC Sensor Test");

  if (!sgp.begin()) {
    Serial.println("SGP40 sensor not found! Check I2C wiring.");
    while (1);
  }

  Serial.println("SGP40 Initialized. Waiting 10s for warm-up...");
  delay(10000);
}

void loop() {
  // Read raw VOC tick count
  uint16_t sraw = sgp.measureRaw();
  
  // Calculate VOC Index (0 to 500) with default 25°C / 50% RH compensation
  int32_t voc_index = sgp.measureVocIndex();

  Serial.print("Raw SRAW_VOC: "); Serial.print(sraw);
  Serial.print(" | VOC Index: "); Serial.println(voc_index);

  delay(1000);
}

Common mistakes

  • Interpreting VOC Index as absolute PPM/PPB: The SGP40 outputs a relative VOC Index (0 to 500) relative to the recent 24-hour baseline. It does not output absolute concentration in PPM or PPB.
  • Forgetting I2C address 0x59: Unlike the SGP30 (0x58), the SGP40 uses I2CI^2C address 0x59.

Notes

  • SGP40 vs SGP30 vs SGP41: SGP30 measures eCO2eCO_2 and TVOCTVOC; SGP40 measures VOC IndexVOC\ Index; SGP41 measures both VOC IndexVOC\ Index and NOx IndexNO_x\ Index.

Assets & downloads