Quantity   Component name
1 × Arduino Nano
1 × MQ2 Gas Sensor Measures Smoke, CO and LPG gas levels
1 × 1S LiPo Battery if using Power Boost (Also can use 2S direct to VIn) Any cheap battery will do
1 × PowerBoost 500 Charger from Adafruit This makes it extremely simple and adds USB charging easily
1 × Dog Chew Toy Enclosure Dollar store enclosure made to tolerate the worst punishment
1 × 433 MHZ Transmitter Super cheap ASK transmitter module