MQ-6 Gas Methane Sensor Module for Arduino

MQ-8 Hydrogen Gas Sensor Module features:
- Main chip: MQ-8 methane sensor and comparator LM393
- Working voltage: 5V
- Current: 150mA
- Digital output: TTL 0/1
- Analog output: analog voltage sensing value
- Quick response features:
- Detection concentration:
  100ppm- 10000ppm hydrogen H2
- Adjustable sensitivity with the potentiometer
- Size: 32mm x 20mmx 18mm

MQ-9 Carbon Monoxide Sensor Module features:
- Main chip: MQ-9 methane sensor and comparator LM393
- Working voltage: 5V
- Current: 150mA
- Digital output: TTL 0/1
- Analog output: analog voltage sensing value
- Quick response features:
- Detection concentration:
   20ppm- 2000ppm carbon monoxide
   500ppm- 10000ppm methane CH4
   500ppm- 10000ppm LPG
- Adjustable sensitivity with the potentiometer
- Size: 32mm x 20mmx 18mm

MQ-4 Gas Methane Sensor Module for Arduino features:
- Main chip: MQ-4 methane sensor and comparator LM393
- Working voltage: 5V
- Current: 150mA
- Digital output: TTL 0/1
- Analog output: analog voltage sensing value
- Quick response features:
- Detection concentration:
200ppm- 10000ppm CH4, natural gas
- Adjustable sensitivity with the potentiometer
- Size: 32mm x 20mmx 18mm

Ethanol alcohol sensor module.
MQ gas sensor uses a small indoor heater with an electrochemical sensor.
When the alcohol molecules in the air comply with the electrode the ethanol "changes" into acetic acid and then more current is produced.
MQ-3 Alcohol Sensor Module Ethanol Breathalyzer features:
- Main chip: alcohol sensor MQ-3 and comparator LM393
- Working voltage: 5V
- Current: 150mA
- Digital output: TTL 0/1
- Analog output: analog voltage sensing value
- Detection concentration:
- 0.05mg/L - 10mg/L
- Quick response features:
- Adjustable sensitivity with the potentiometer
- Size: 32mm x 20mmx 18mm

Air quality sensor with high precision whose SDS011 uses laser dispersion to detect particle concentration between 0.3 and 10 um in the air.

With digital output by USB (UART) and built-in fan. It is a powerful sensor, fast (response less than 10s), accurate and reliable.

MQ-7 Carbon Monoxide Sensor Module. The sensor detects the concentration of CO (carbon monoxide) and flammable gases. It has a goldpin connector raster 2.54 mm. It is powered by 5 V. It has digital and analogue outputs, which makes it compatible with most runtime modules including Arduino.

MQ-2 Gas and Smoke Module Sensor Detector Methane Propane Butane LPG features:
- Main chip: MQ-2 flammable gas and smoke sensor and comparator LM393
- Working voltage: 5V
- Current: 150mA
- Digital output: TTL 0/1
- Analog output: analog voltage sensing value
- Quick response features:
- Concentration detection:
  200ppm - 5000ppm LPG, propane
  300ppm - 5000ppm butane
  5000ppm - 20000ppm methane
  300ppm - 5000ppm H2
  100ppm -2000ppm alcohol
- Adjustable sensitivity with the potentiometer
- Size: 32mm x 20mmx 18mm

MG-5 Gas Methane Sensor Module for Arduino features:
- Main chip: MQ-5 natural gas sensor and comparator LM393
- Working voltage: 5V
- Current: 150mA
- Digital output: TTL 0/1
- Analog output: analog voltage sensing value
- Quick response features:
- Detection concentration:
- 200ppm - 10000ppm LPG, LNG, natural gas, propane,
- Adjustable sensitivity with the potentiometer
- Size: 32mm x 20mmx 18mm

High sensitivity to Ammonia (NH3), Nitrogen oxides (NOx), Alcohol, Sulphides, Benzene (C6H6), CO2, smoke and other harmful gases.  The MQ-135 sensor is to sensible for other gasses in the air so that is not possible to get good values for CO2 from it.
MQ-135 Air Quality Sensor features:
- Main chip: MQ-135 natural gas sensor and comparator LM393
- Working voltage: 5V
- Current: 150mA
- Digital output: TTL 0/1
- Analog output: analog voltage sensing value
- Quick response features:
- Detection concentration:
   10ppm - 300ppm NH3
   10ppm - 1000ppm Benzene
   10ppm - 300ppm Alcohol
- Adjustable sensitivity with the potentiometer
- Size: 32mm x 20mmx 18mm

The ZP07-MP503 air quality module offers high sensitivity with low power consumption and long life. Calibration before shipment from 10 seconds to 3 minutes max. with automatic warm-up function. Automatic fault check.