Do I need radon measurement?

Depends on your location. The EPA recommends testing homes in radon-prone areas. Airthings is the only consumer sensor with radon. Alternatively, you can order a professional test kit.

How accurate are cheap CO2 sensors?

SenseAir S8 (used in AirGradient) is an NDIR sensor with ±40ppm accuracy - that's industry standard. Cheap MQ-135 'CO2 sensors' actually measure VOC and are inaccurate. Avoid them.

Why is my CO2 level high at night?

A closed bedroom quickly accumulates CO2 from your breathing. One person exhales ~200 ml CO2 per minute. Keep the door open or use ventilation!

What's the difference between PM2.5 and PM10?

PM2.5 are particles under 2.5 micrometers (most dangerous - penetrate deep into lungs). PM10 are under 10 micrometers. PM2.5 is the most important health measurement.

Can I control my HRV with CO2?

Yes! Many HRV/ERV systems (Zehnder, Broan, Panasonic) can be controlled via 0-10V signal or modbus. Use ESPHome to send signals based on CO2 level.

Smart Air Quality

Health CO2 Automation

Poor indoor air quality can cause headaches, fatigue, concentration problems and long-term health issues. With smart air quality monitoring you can track CO2, particles and VOC - and automate ventilation.

🌬️ Air Quality Overview

What Should You Measure?

Parameter	Danger Level	Symptoms	Sensor
CO2	Over 1000 ppm	Headache, fatigue, poor concentration	SenseAir S8
PM2.5	Over 35 µg/m³	Respiratory problems, allergies	Plantower PMS5003
VOC	Over 500 ppb	Headache, dizziness	SGP30, SGP41
Radon	Over 4 pCi/L	Lung cancer (long-term)	Airthings
Humidity	Under 30% / Over 60%	Dry skin, mold	SHT30, DHT22

Product Comparison

Product	HA Integration	CO2	PM2.5	VOC	Radon	Price
Airthings View Plus	✅ Cloud API	✅	✅	✅	✅	💰💰💰
Airthings Wave Plus	✅ BLE	✅	❌	✅	✅	💰💰
Awair Element	✅ Local API	✅	✅	✅	❌	💰💰
AirGradient ONE	✅ ESPHome	✅	✅	✅	❌	💰💰
ESPHome DIY	✅ Local	✅	✅	⚠️	❌	💰

📊 Airthings (Native HA - 3,034 users)

Airthings View Plus: ~$300 Airthings Wave Plus: ~$230 Airthings Wave Mini: ~$100

Specialized in radon measurement:

✅ Only consumer sensor with radon
✅ CO2, VOC, temperature, humidity
✅ View Plus: also PM2.5
✅ Cloud API + BLE integration
✅ Battery: up to 2 years
⚠️ Cloud-dependent (API)
⚠️ BLE only for Wave series

Cloud API Integration (View Plus + all)

# Settings → Devices → Add Integration
# Search "Airthings"

# Requires Airthings API credentials:
# 1. Go to dashboard.airthings.com
# 2. Integrations → API → Request API Client
# 3. Name: "Home Assistant"
# 4. Resource Scope: read:device:current_values
# 5. Access Type: Confidential
# 6. Enable: On
# 7. Copy ID and Secret to HA

# Entities created:
# - sensor.airthings_co2
# - sensor.airthings_radon_short_term
# - sensor.airthings_radon_long_term
# - sensor.airthings_voc
# - sensor.airthings_pm25 (View Plus)
# - sensor.airthings_temperature
# - sensor.airthings_humidity
# - sensor.airthings_pressure

BLE Integration (Wave series - local!)

# Requires Bluetooth in HA
# (USB dongle or ESP32 Bluetooth Proxy)

# Settings → Devices → Add Integration
# Search "Airthings BLE"

# Autodiscover finds Wave devices
# Serial number (last 6 digits) used for ID

# Benefits of BLE:
# - No cloud dependency
# - Faster updates
# - Works offline

Ventilation Based on CO2

automation:
  # Warn on high CO2
  - alias: "Air Quality - High CO2"
    trigger:
      - platform: numeric_state
        entity_id: sensor.airthings_co2
        above: 1000
        for: "00:10:00"
    action:
      - service: notify.mobile_app
        data:
          title: "🌬️ Open a window!"
          message: >
            CO2 level: {{ states('sensor.airthings_co2') }} ppm
            The air is stuffy - time to ventilate.

  # Radon warning
  - alias: "Air Quality - Radon Warning"
    trigger:
      - platform: numeric_state
        entity_id: sensor.airthings_radon_short_term
        above: 4  # pCi/L (US standard)
    action:
      - service: notify.mobile_app
        data:
          title: "☢️ High Radon!"
          message: >
            Radon: {{ states('sensor.airthings_radon_short_term') }} pCi/L
            Consider ventilation or radon mitigation.
          data:
            push:
              sound:
                name: "alarm.caf"

  # Automatic ventilation
  - alias: "Air Quality - Start Ventilator"
    trigger:
      - platform: numeric_state
        entity_id: sensor.airthings_co2
        above: 800
    action:
      - service: fan.turn_on
        entity_id: fan.ventilation
      - service: notify.mobile_app
        data:
          message: "Ventilator started due to CO2"

  - alias: "Air Quality - Stop Ventilator"
    trigger:
      - platform: numeric_state
        entity_id: sensor.airthings_co2
        below: 600
    action:
      - service: fan.turn_off
        entity_id: fan.ventilation

Buy: Airthings.com, Amazon

🌿 Awair Element (Local API - 1,468 users)

Overview
Home Assistant

Price: ~$200

Local API without cloud:

✅ CO2 (0-4000 ppm)
✅ PM2.5 particles
✅ VOC (total volatile organic compounds)
✅ Temperature and humidity
✅ Local API (no cloud required!)
✅ Beautiful display with score
❌ No radon
❌ Requires power (USB-C)

Native Integration

# Settings → Devices → Add Integration
# Search "Awair"

# Two methods:

# 1. LOCAL (recommended):
# - Enable Local API in Awair app
# - HA autodiscover finds device
# - Polling every 30 seconds

# 2. CLOUD:
# - Requires Awair Developer token
# - developer.getawair.com
# - Up to 24 hours for approval
# - Polling every 5 minutes

# Entities:
# - sensor.awair_element_co2
# - sensor.awair_element_pm25
# - sensor.awair_element_voc
# - sensor.awair_element_temperature
# - sensor.awair_element_humidity
# - sensor.awair_element_score

Buy: Awair.com, Amazon

🔧 AirGradient ONE (ESPHome - Recommended DIY)

Price: ~$150 (assembled) DIY kit: ~$95

Open source air quality monitor:

✅ CO2 (SenseAir S8 - NDIR)
✅ PM2.5/PM10 (Plantower PMS5003)
✅ VOC + NOx (Sensirion SGP41)
✅ Temperature and humidity
✅ ESPHome firmware (100% local)
✅ Color LED bar for quick status
✅ OLED display
❌ No radon
❌ Requires power (USB-C)

Native AirGradient Integration (new!)

# Since June 2024 AirGradient has
# a native HA integration!

# Settings → Devices → Add Integration
# Search "AirGradient"

# Autodiscover finds devices on network

ESPHome (full control)

# Alternative: Flash ESPHome firmware
# for 100% local control

esphome:
  name: airgradient-one
  platform: ESP32
  board: esp32-c3-devkitm-1

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

api:
  encryption:
    key: !secret api_encryption_key

# I2C for sensors
i2c:
  sda: GPIO7
  scl: GPIO6

# UART for CO2 and PM
uart:
  - id: uart_pm
    rx_pin: GPIO20
    tx_pin: GPIO21
    baud_rate: 9600
  - id: uart_co2
    rx_pin: GPIO0
    tx_pin: GPIO1
    baud_rate: 9600

sensor:
  # CO2 - SenseAir S8
  - platform: senseair
    uart_id: uart_co2
    co2:
      name: "CO2"
      id: co2
    update_interval: 60s

  # PM2.5 - Plantower
  - platform: pmsx003
    type: PMSX003
    uart_id: uart_pm
    pm_2_5:
      name: "PM2.5"
      id: pm25
    pm_10_0:
      name: "PM10"

  # Temperature/Humidity
  - platform: sht3xd
    temperature:
      name: "Temperature"
    humidity:
      name: "Humidity"
    address: 0x44

  # VOC Index
  - platform: sgp4x
    voc:
      name: "VOC Index"
    nox:
      name: "NOx Index"

Build Yourself (~$60-80)

Components:

ESP8266 D1 Mini (~$8)
SenseAir S8 CO2 sensor (~$45)
Plantower PMS5003 (~$20)
SHT30 temp/humidity (~$4)
0.96” OLED display (~$5)
3D printed case (free file)

Total: ~$82

# Basic ESPHome config for DIY
esphome:
  name: air-quality-diy

esp8266:
  board: d1_mini

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

api:

i2c:
  sda: D2
  scl: D1

uart:
  - rx_pin: D5
    tx_pin: D6
    baud_rate: 9600
    id: uart_pm
  - rx_pin: D7
    tx_pin: D8
    baud_rate: 9600
    id: uart_co2

sensor:
  - platform: senseair
    uart_id: uart_co2
    co2:
      name: "CO2"
    update_interval: 60s

  - platform: pmsx003
    type: PMSX003
    uart_id: uart_pm
    pm_2_5:
      name: "PM2.5"

  - platform: sht3xd
    temperature:
      name: "Temperature"
    humidity:
      name: "Humidity"
    address: 0x44

display:
  - platform: ssd1306_i2c
    model: "SSD1306 128x64"
    address: 0x3C
    lambda: |-
      it.printf(0, 0, id(font1), "CO2: %.0f ppm", id(co2).state);
      it.printf(0, 16, id(font1), "PM2.5: %.0f", id(pm25).state);

Resources:

Buy: AirGradient.com, DIY components from AliExpress

📈 CO2 Levels Guide

CO2 ppm	Status	Effect
400-600	🟢 Optimal	Fresh air, good concentration
600-800	🟡 Acceptable	Slightly reduced attention
800-1000	🟠 Moderate	Headache, fatigue begins
1000-1500	🔴 Poor	Clear fatigue, concentration issues
1500-2000	🟣 Very poor	Strong headache, dizziness
>2000	⚫ Dangerous	Nausea, heart palpitations

🤖 Complete Automation Suite

automation:
  # ===== CO2 BASED VENTILATION =====

  # Smart ventilator control
  - alias: "Air - Adaptive Ventilation"
    trigger:
      - platform: state
        entity_id: sensor.airgradient_co2
    action:
      - choose:
          # High CO2 - full speed
          - conditions:
              - condition: numeric_state
                entity_id: sensor.airgradient_co2
                above: 1000
            sequence:
              - service: fan.set_percentage
                entity_id: fan.ventilation
                data:
                  percentage: 100
          # Moderate CO2 - medium
          - conditions:
              - condition: numeric_state
                entity_id: sensor.airgradient_co2
                above: 800
            sequence:
              - service: fan.set_percentage
                entity_id: fan.ventilation
                data:
                  percentage: 50
          # Normal - turn off
          - conditions:
              - condition: numeric_state
                entity_id: sensor.airgradient_co2
                below: 600
            sequence:
              - service: fan.turn_off
                entity_id: fan.ventilation

  # ===== PM2.5 WARNINGS =====

  - alias: "Air - High PM2.5"
    trigger:
      - platform: numeric_state
        entity_id: sensor.airgradient_pm25
        above: 35
        for: "00:15:00"
    action:
      - service: notify.mobile_app
        data:
          title: "😷 Poor air quality"
          message: >
            PM2.5: {{ states('sensor.airgradient_pm25') }} µg/m³
            Consider turning on air purifier.
      - service: switch.turn_on
        entity_id: switch.air_purifier

  - alias: "Air - PM2.5 OK again"
    trigger:
      - platform: numeric_state
        entity_id: sensor.airgradient_pm25
        below: 12
        for: "00:30:00"
    action:
      - service: switch.turn_off
        entity_id: switch.air_purifier

  # ===== VOC MONITORING =====

  - alias: "Air - High VOC"
    trigger:
      - platform: numeric_state
        entity_id: sensor.airgradient_voc_index
        above: 250
    action:
      - service: notify.mobile_app
        data:
          title: "🧪 High VOC"
          message: >
            VOC Index: {{ states('sensor.airgradient_voc_index') }}
            Ventilate - possible chemicals in the air.

  # ===== BEDROOM AUTOMATION =====

  - alias: "Air - Bedroom Night"
    trigger:
      - platform: time
        at: "22:00:00"
    action:
      - service: fan.turn_on
        entity_id: fan.bedroom_ventilation
        data:
          percentage: 30
      - service: notify.mobile_app
        data:
          message: "Night ventilation started"

  - alias: "Air - Bedroom Morning"
    trigger:
      - platform: time
        at: "07:00:00"
    action:
      - if:
          - condition: numeric_state
            entity_id: sensor.bedroom_co2
            above: 800
        then:
          - service: fan.set_percentage
            entity_id: fan.bedroom_ventilation
            data:
              percentage: 100
          - delay: "00:30:00"
      - service: fan.turn_off
        entity_id: fan.bedroom_ventilation

📊 Dashboard

type: vertical-stack
cards:
  # Air quality gauge
  - type: gauge
    entity: sensor.airgradient_co2
    name: "CO2"
    min: 400
    max: 2000
    severity:
      green: 400
      yellow: 800
      red: 1000

  # All measurements
  - type: entities
    title: "🌬️ Air Quality"
    entities:
      - entity: sensor.airgradient_co2
        name: "CO2"
        icon: mdi:molecule-co2
      - entity: sensor.airgradient_pm25
        name: "PM2.5"
        icon: mdi:blur
      - entity: sensor.airgradient_voc_index
        name: "VOC Index"
        icon: mdi:air-filter
      - entity: sensor.airgradient_temperature
        name: "Temperature"
      - entity: sensor.airgradient_humidity
        name: "Humidity"

  # History
  - type: history-graph
    title: "CO2 (24 hours)"
    entities:
      - entity: sensor.airgradient_co2
    hours_to_show: 24

🛒 Buying Strategy

Budget DIY (~$60)

ESP8266 D1 Mini (~$8)
SenseAir S8 (~$45)
SHT30 (~$4)
Total: ~$57 (CO2 only)

Standard AirGradient (~$150)

AirGradient ONE kit (~$150)
Includes CO2, PM2.5, VOC, temp, humidity
Total: ~$150

Premium Airthings (~$300)

Airthings View Plus (~$300)
Includes everything + Radon
Total: ~$300

❓ Frequently Asked Questions

Ofte stillede spørgsmål

Do I need radon measurement?: Depends on your location. The EPA recommends testing homes in radon-prone areas. Airthings is the only consumer sensor with radon. Alternatively, you can order a professional test kit.
How accurate are cheap CO2 sensors?: SenseAir S8 (used in AirGradient) is an NDIR sensor with ±40ppm accuracy - that's industry standard. Cheap MQ-135 'CO2 sensors' actually measure VOC and are inaccurate. Avoid them.
Why is my CO2 level high at night?: A closed bedroom quickly accumulates CO2 from your breathing. One person exhales ~200 ml CO2 per minute. Keep the door open or use ventilation!
What's the difference between PM2.5 and PM10?: PM2.5 are particles under 2.5 micrometers (most dangerous - penetrate deep into lungs). PM10 are under 10 micrometers. PM2.5 is the most important health measurement.
Can I control my HRV with CO2?: Yes! Many HRV/ERV systems (Zehnder, Broan, Panasonic) can be controlled via 0-10V signal or modbus. Use ESPHome to send signals based on CO2 level.

📚 Next Steps

Smart Water

Protect against water damage.

See guide →

ESP32 Projects

Build more sensors yourself.