Overview

The CCS811 is an ultra-low power digital metal-oxide (MOX) gas sensor solution manufactured by ams OSRAM for monitoring indoor air quality (IAQ). It integrates a micro-hotplate sensor element along with a dedicated 8-bit microcontroller that processes raw sensor resistance values and calculates Total Volatile Organic Compounds (TVOC in parts per billion, ppb) and equivalent carbon dioxide ($\text{eCO}_2$ in parts per million, ppm).

Communicating over $I^2C$, the CCS811 supports environmental temperature and humidity compensation inputs (from external sensors like the BME280 or HDC1080) to improve baseline stability. It is widely incorporated into home automation systems, air purifiers, ESPHome nodes, and indoor environment monitors.

Quick reference

Pinout

Breakout modules feature a 7-pin or 8-pin 0.1" (2.54 mm) header:

Specifications

Register map

Wiring

Example

#include <Wire.h>
#include "Adafruit_CCS811.h"

Adafruit_CCS811 ccs;

void setup() {
  Serial.begin(115200);
  Serial.println("Initializing CCS811 Air Quality Sensor...");

  if (!ccs.begin(0x5A)) {
    Serial.println("Failed to start CCS811! Ensure WAKE pin is connected to GND.");
    while (1);
  }

  // Wait for sensor to become ready
  while (!ccs.available());
  Serial.println("CCS811 ready.");
}

void loop() {
  if (ccs.available()) {
    if (!ccs.readData()) {
      Serial.print("CO2: ");
      Serial.print(ccs.geteCO2());
      Serial.print(" ppm | TVOC: ");
      Serial.print(ccs.getTVOC());
      Serial.println(" ppb");
    } else {
      Serial.println("Error reading CCS811 data!");
    }
  }
  delay(1000);
}

Common mistakes

• Leaving WAKE floating: The sensor ignores all $I^2C$ commands unless WAKE is grounded.
• Conflating $\text{eCO}_2$ with true NDIR $\text{CO}_2$: The CCS811 estimates equivalent $\text{CO}_2$ ($\text{eCO}_2$) by measuring hydrogen and volatile organic gas levels, assuming human breath correlates with VOCs. It does not contain an NDIR optical absorption cell and will not measure pure $\text{CO}_2$ accurately in non-human-occupied spaces.
• Skipping initial 48-hour burn-in: MOX sensor materials undergo initial resistance stabilization. Readings during the first 48 hours of power-on exhibit drift.
• Forgetting temperature/humidity compensation: Supplying live temperature and humidity values to ENV_DATA significantly improves accuracy in changing ambient environments.

Notes

• CCS811 vs SGP30: Sensirion SGP30 and ams CCS811 are direct competitors in the metal-oxide indoor air quality market.