Ideas for Areas to Explore

• Compare the MiCS-5524 with the i2c Sensirion SGP30 and AMS CCS811.
• Monitor alcohol fermentation processes.
• Add a sensor to a mobile robot to seek out or map gases.
• Investigate other MQ sensors to determine their ability to distinguish between different flammable gases. Compare with others like Figaro.
• Detect local graffiti artists using aerosol paints by sampling outdoor air.
• Test other household products like nail polish remover (ketones), antifreeze (diols), vinegar (carboxylic acid) and old fashioned smelling salts (ammonia).
• Investigate different power supplies to look for effects of power supply related noise and possible compensation techniques for low frequency noise. An extra analogue input (with appropriate voltage scaling to 3.3V) could be used to monitor/check 5V power.
• Check behaviour of sensors with low power supply voltage. The analogue output appears to go up substantially, presumably due to the lower heater temperature.
• Explore other sensors:
  • A zinc-air battery as a "sensor" to measure oxygen, see The World's Cheapest Oxygen Sensor.
  • The Sensirion SCD-30 is an NDIR-based, true carbon dioxide sensor.
• Look at environmental monitoring using the trio of gas sensors on the MiCS-6814: Instructables: Using the Pimoroni Enviro+ FeatherWing With the Adafruit Feather NRF52840 Express.
• Build an "electronic nose" (olfaction) using an array of different sensors, see Michael Madsen's very thorough, cheap electronic nose research.

Related Projects

• LED breath stats mask

Further Reading

• Carbon Monoxide - the Silent Killer (pdf)
• Figaro Eningeering: Gas Sensor Principles
• NY Times: Cheaper Battery Is Unveiled as a Step to a Carbon-Free Grid
  
• The Economist: A new device can identify air travellers carrying an infectious disease
• Bosch BME680 Environmental Sensor demo (YouTube) -  the STEMMA QT/i2c connected Adafruit BME680 - Temperature, Humidity, Pressure and Gas (MOX) Sensor in action.
• Metal Oxide (MOX) Gas Sensors: Sensitivity and Influencing Factors (complex stuff but has good pictures!)