This is a Home/Flat ventilation system.

For measuring rooms air quality it uses two gas sensors MQ-9 and MQ-135 also a Thermistor for measuring temperature. Displays gas value (unitless) and temperature (celsius) on a I2C 128x32 SSD1306 driver OLED display. Has a two buttons: first button -- Toggles ON/OFF the display second button -- Turns on the fans for a period of time

Circuit:

What it does?

Automatically turns the fans ON, when the air quality goes bad (user inputs the values)
User can turn the fans for a period of time, the remaining time is displayed on the LCD
Toggle ON/OFF the display -- Why should it run always.

watch a demo video below:

Demo video link only one sensor in demo :(

Technologies used:

For measuring temperature with a Thermistor, Steinhart–Hart equation was used
for the OLED display u8x8 library was used